How much her shard has influenced her personality is an open question.
She built her life, from a very young age, around making sure that Zion did not complete his cycle.
Contessa choose her path from when she was a young girl and followed it unflinching for decades. Thanks to her power it is reasonable to assume that like her opponent she was shielded from the psychological stimulation that lends itself to maturity.
Despite being extremely powerful, Contessa does not lead Cauldron and instead acts as Doctor Mother's bodyguard and right-hand woman.
She is one of the most powerful parahumans in existence and is known as "her" or "the Boogeyman" to people high-ranked enough in the Protectorate to know about her. One Protectorate cape classifies her as "Thinker. Don't worry about the number. Just run."
Contessa is a pale-skinned woman with black hair described as "somewhere between wavy and curly", worn a little longer than shoulder length. On at least one occasion, she wore it in a loose ponytail. She was pretty, but didn't wear obvious makeup.
As a child, she generally wore a school uniform. As an adult, she wears a tailored black suit with a white dress shirt and a black tie and a fedora.
Contessa's power allows her to see the adaptable steps she needs to take to succeed at nearly any given task and execute them perfectly. Its applications include combat, communication, social situations, Cauldron's long-term plans, and how to set conditions for trigger events. Through a series of questions (see below) she is able to use it to the utmost. Though almost unparaleled in power even it has limits or restrictions. (see below)
She can default to following the path letting her shard take over. Thus putting herself out of range for many powers.
When trying to persuade someone it gives her the savoir faire necessary to succeed.
To get the most out of her power she asks herself various questions at the start of each day, and various questions before a mission to ensure success. This lets her keep to the path to defeat Zion and provides her with protection against masters and strangers.
Her power also provides her with excellent information gathering abilities provided the right questions are asked.
Her power does not protect her from her own human error but the right questions can reduce this likelihood.
While Contessa can execute most tasks, she has some blind spots. She cannot directly use her power on an Entity, the Endbringers, powerful capes like Glaistig Uaine and Eidolon, and intricate interactions of powers She can still somewhat predict their actions by considering a hypothetical situation.
Her power does not allow her to Tinker rather it gives her the ability to handle tinkertech while avoiding misfires
and lets her damage or subvert it just enough for it to do what she wants.
Contessa was born as Fortuna on another earth that Eden collided with. When she was a child, several people in her village triggered by consuming food and drink contaminated with parts of Eden following the entity's crash-landing. Fortuna's trigger event included a vision of Eden and Scion's plans to sow conflict and destroy humanity, and she set about finding and killing the entity with a power that was still unrestricted.
The entity, realising what she was trying to do, restricted her power so that it could not be used against Entities. However, Fortuna had already seen the steps required to kill the Entity, and with the help of a woman who would later call herself 'the Doctor,' Fortuna managed to stop the entity from killing her and reclaiming the critical shard. The Doctor, armed with a knife and directions both given by Fortuna, managed to stab the entity in a critical location, rendering it effectively brain dead.
The Doctor and Fortuna founded Cauldron with the sole purpose of stopping Eden's partner entity, Scion. They harvested Eden's corpse for powers, which they were able to grant to other people. Ashamed of the human experimentation she had to perform to improve the power formula, Fortuna took the name Contessa out of respect to her parents and a desire to avoid sullying the name they gave her. 
Through the years Contessa as she was now served as the doctor's bodyguard, whenever they went on dangerous assignments.
Keeps the details revealed during the Echidna battle hush hush. Was transferred back to Cauldron's home base to ensure that there were no escapes, the events of the Echidna event were allowed to leak out.
Bonesaw when masquerading as Riley is confronted by Contessa during the time skip while the rest of the Slaughterhouse Nine are in stasis. Contessa prompts Bonesaw in her initial thoughts to betray the Nine with a conversation about the distinction between her and her passenger.
Contessa helped coordinate Cauldron's response to Scion. Doctor Mother requested that she find three candidates for some vials that had historically yielded very strong powers, but Contessa was intercepted by attacking Irregulars before she was able to leave the facility. One of the Irregulars, Mantellum, was able to block Contessa's power, forcing her to flee Cauldron's offices and fake her death.
After returning to the facility and discovering the Doctor is dead, Contessa provided Cauldron's contingency plans to Teacher and assumed second-in-command of his organization.
Following Scion's death, Contessa tracked down Khepri and, after a brief conversation aided by her abilities, disabled her shard with two bullets.
Following an attempt to stop relying on her power Fortuna was captured and imprisoned by Teacher's branch of Cauldron. During The Wardens' assault on the compound she was freed by Imp and Breakthrough. She led them to victory over Teacher, and in the final confrontation with Teacher rejected his methods, which led to him scrapping his endgame plans and running away.
In subsequent days she joined Citrine as a consultant.
When Scion examined Contessa, he "saw a shard that wasn’t its own, but wasn’t dead"; normally, shards from Eden are dead. This may indicate that Contessa's shard is still linked to Abaddon, since Eden was in the process of integrating it when she crash-landed and lost it.
↑I could only think of one powerful individual who was on a par with the others she’d named. Contessa and Glaistig Uaine were easily twelves or higher on the power-ratings scale, and I could look to others with powers in that neighborhood to figure out who she was referring to. Panacea, Labyrinth… - Excerpt from Extinction 27.4
↑Not what I’d meant. “Giving too much power to wrong people. To bullies. With powers, bullies without.”
She gave me a slightly surprised look at that. “I don’t see that applying to Scion.”
“He doesn’t factor? He isn’t a consideration, at the end?”
“Fighting him… always more about us than about him. Not a consideration.”
“And the person who played the biggest role in stopping him doesn’t give him a second thought,” she said. There was a note of emotion in her voice. She was gripping the gun handle tightly enough that her knuckles turned white, but her expression wasn’t an angry one.
I didn’t respond. I felt like it might have been rude to. We all had our demons, our burdens, and this was hers. - Excerpt from Speck 30.7
↑Easier to have an adult handling the negotiating and person-to-person interaction. Fortuna was young, and people wouldn’t be so inclined to drink a strange substance offered by a child.
[include Doctor mother]
- Excerpt from Interlude 29
↑ 6.06.16.2She was older, but not old. Maybe my dad's age, maybe a little younger. Pretty, in a very natural way. She didn't wear any obvious makeup, and her black hair was somewhere between wavy and curly, a little longer than shoulder length. Her features French or Italian, if I had to guess. She wore only a simple black suit that had been tailored to fit her body, with a narrow black tie and a white dress shirt. What got me were the eyes. There was no kindness in them. - [ Excerpt] from Crushed 24.2
↑ 7.07.1The rectangular portal closed, and I was left staring at a wall. I turned to see the woman in the suit. She was tidy, her hair tied back in a loose ponytail with strands tracing the side of her face, and she held a fedora in one hand. The hat was beaded with moisture. Another excursion she'd made before reaching out to me? - Scarab 25.5
The woman looked supremely at ease as she took a seat opposite David. The teenage girl who accompanied her was just as confident. Here and there in the little cafe, people gave them dirty looks.
The woman was black, dressed all in white, the girl wore a private school uniform and held a notebook and fountain pen. - 27.x (Interlude, Eidolon)
↑Rebecca stirred, turning around to see who was speaking. A black woman with long hair in a doctor's get-up was messing with the IV bag. But… no name tag. And there was a teenage girl with pale skin and dark hair standing behind her, wearing knee-high socks, a black pleated skirt and white dress shirt. "You're not one of my doctors." - Interlude 15.z
↑A young woman, dark-haired, wearing a suit and fedora, with luggage on wheels. - Interlude 18.f
↑She could see each individual step, looking forward to see what it entailed. She could see it evolve as time passed, accounting for her starting it later.
↑Torrieltar: Path to Victory comes with a sort of autopilot, right? Do we know what kind of limits that has? If, for example, a telepath was inflicting what would normally be debilitating psychological pain, would Path to Victory's autopilot help to power through that?
Wildbow: Autopilot yes (defaulting control to shard with faster-than-human processing), if her body remained functional then she'd basically move forward in a haze of PtVness. - Wildbow on Reddit
↑Torrieltar: How fast can Path to Victory react to unforeseen changes?
Wildbow: All changes are foreseen, as a rule. Can't cite anything, but there's a line that sorta appears in the story, where you run into the perfects (perfect defense, perfect offense) and stuff gets fucky - and the rule of thumb is that 'unless your ability beats -everything-, it doesn't beat this'. For processing power Contessa's ability would be on this level (as with Flechette's Sting, Clockblocker's inviolability, Siberian's invulnerability). - Wildbow on Reddit
↑Fog approached. A wall of it, moving down the corridor. She could see normally, but the effect on her powers was absolute. It was impossible to make out any steps that moved within the fog. [...] She ducked. “-have a perception blocker, [...] They’ve got a thinker, I think, they planned this ahead of time, knowing I wouldn’t pick up on their presence.” [...] This ‘Mantellum’ had been close enough that he should have been able to block her power. He hadn’t.
Because he’d been on the other side of the portal. The power didn’t cross dimensional boundaries. - Excerpt from Interlude 29
↑Jack beats Citrine, Siberian, Grey Boy (until interfered with by outside sources), Number Man and arguably Contessa. - Wildbow on Reddit
↑Torrieltar: Has Contessa ever fought combat precogs before (strong ones, more along the lines of atium than the Force)? If so, what was the result?
Wildbow: Limited examples in story. I have stated in word of god that she's trumped/matched by Jack Slash, but that's a unique case and not really combat precog so much as shard-one-upmanship. - Wildbow on Reddit
↑ 19.019.1Torrieltar:How hard is it to trick Contessa into asking her Path to Victory the wrong question?
Wildbow: Theoretically possible/doable. But if you're doing it by any measure that's blatant, you're working against the vast, fast processing engine that is her shard. Given time, she pre-asks about deception, mind control, AoE and other obstacles her power wouldn't effectively fight against. - Wildbow on Reddit
↑RazorSmile:It's not rocket surgery. A sufficiently wide and dense area-effect attack will either kill her, force her to leave or, if her power has that much range, keep her from showing up in the first place.
Wildbow: Unless she, before she headed out the door, posed herself the scenario: Contessa: "What do I need to do to come back successful from this mission?" (Psst. Don't walk into the sufficiently wide, sufficiently dense area-effect attack. Here's a workaround). "Goodie." - Wildbow on RPG.net
↑People began preparing to leave, gathering stuff together.
“No,” I could overhear Contessa saying, “I ask myself several questions before I go anywhere, and one pertains to strangers. Stay behind.”
Imp appeared next to her. She walked back to us with a very dejected appearance. - Excerpt from Extinction 27.2
↑“I can’t defeat [Teacher], spare as many of your allies’ lives as possible, and save the lives of people in the city. Not as I or my power understand circumstances, and my power understands everything outside of the blind spots that are Teacher, Valkyrie, the Simurgh, and two broken triggers that authorities aren’t aware happened.” [...] Imp groaned. “You’re making me look awful here. I promised these guys one hundred percent victory.”
“If you’d found me sooner, then I could have.”
“How do you know all of this if you were in a coma?” Sveta asked. “The Simurgh, who’s where, what Custodian is doing?”
“I’m finding it out as I explain it to you. I asked my power for the path to provide the explanation I need to give, that serves the purpose of filling me in on present circumstance. When you talk among yourselves, I’m asking my usual questions.”
“Like how you can avoid being fucked over by a Stranger or Master in the next day or whatever,” Imp said.
↑One point to Foxtail on relevant quotes. Closest answer, really. Tinkering may be real science, but it's real science conducted by digging deep into shard senses and networks. Contessa can do this to an extent, but not to the point that she could just go full Tinker-9001. - tinker material
↑Whatever she was doing was working. When I switched my view away from the map and to Kenzie’s diagram of the facility’s infrastructure, I could see that Kenzie was making headway. I could see some messages between her and the computer console Contessa was at.
I cannot work with tinkertech or tinker code but I can give you the boot passwords to the server terminals. Old data is still on the systems, heavily encrypted.
i reset & access old system archetecture in at boot lvl???
↑In the midst of the Kulshedra, I could sense moving air currents. A woman emerged from thin air, from a place cooler than the interior of the ship. The civilians we’d rescued shrieked and backed away from her. She didn’t respond, barely reacted. Someone with long, dark hair and a suit. She fixed her cuffs, then moved with purpose.
But I found myself less fixated on her than on her surroundings. Oddly enough, I could feel a different structure behind the woman, a hallway. [...] Satyr didn’t speak. He glanced at the ship. He couldn’t see from the angle he’d approached, but the woman inside had pulled the lever, and the door at the back was slowly closing. [...] “Kul-,” I gasped out.
The woman turned and walked up to the ruined nose of the craft, and began threading wires together. She didn’t even flinch as sparks flared between them. She was measured, even patient, as she worked at fixing the panel. When she was done, she tapped something out on the broken, unlit touch panel.
“Kulshedra, shut down,” I managed.
The pillar rose from the top of the box, freeing the upper part of the box’s door.
“Kulshedra, contact Dragon,” I tried.
“Dragon is currently unable to reply.”
The woman tapped out another code, and the clamps on the bottom came open, freeing the bottom.
Yet another code typed out, and the system spoke, “Type two safety override accepted.”
The woman in the ship struck a single button. The A.I. spoke, “Call ended.”
“Kulshedra, call Chevalier,” I repeated.
The woman inside typed out a final code, and the door of the box opened, releasing Pretender.
And then she spoke, and I could hear through the bugs that surrounded her. “The Doctor will see you now.”
“Right-o,” Pretender said. “Gotta be better than the Birdcage.”
They stepped through the gateway that led to the cool, air-conditioned hallway, and then they were gone, the butterflies in the hallway no longer in my reach.
I felt my blood pumping, roaring in my ears. “They got him. They collected Pretender.”
“Her. The shooter’s partner. Cauldron.” I clenched my fist. “Rime’s down. We have to help her.” [...] Arbiter looked from her phone to Prefab. “Dragon collapsed just before this began. She was meeting a Las Vegas Rogue.”
“Yeah,” I said. I thought of the woman who’d been so handy with the computer. The censor, the bogeyman. They’d taken out Rime, no doubt because she could have sealed the box behind a wall of ice.
Yet they hadn’t taken out Prefab, who could have done much the same thing.