Alvis is a bon vivant, hedonistic kinda guy, who's only real values are a vague notion of "good", how awesome magic is, and strong business sense. So he was a pretty hands-off, laissez faire kind of father. Almost absentee really, leaving his kids to pretty much raise themselves, with occasional "words of widsom" or last minute bonding experiences. I mean, he meant well, but really, not #1 Dad tankard material. Mom was always kind and caring, affectionate, but also pretty spacey and not-all-there. She also had a tendency to wander off for days at a time, and when asked about it, Alvis would just quietly chuckle, smoking his pipe and reading his paper. "Welp, that's Mom for you."
This annoyed the hell out of Ali, and as a teenager she rebelled against it. So when the Priory started preaching about the Pillar of Karmir, the cycle of life and death, how the two are inexorably entwined, and how undeath spits in the face of this, Ali ate it up. She finally had a bedrock to build from, and so she willfully became totally and completely indoctrinated (to the point where it unnerved even her instructors).
The Priory had finally given her her life's purpose. Her raison d'etre. And that's how she heads off into the world, a person who knows, down to the core of her being, exactly what her purpose in life is. She exists to kill Katriona and eradicate all her ilk from the face of Teraus.
Of course, she isn't foolhardy. She understands her limits, knows her strengths and her weaknesses. She won't kill Katriona by the end of the week; this is what she's devoted her entire life to. Ali might not be book smart, but she is highly pragmatic and rational. A common-sense kinda girl.
And while she's morally good, she is also single mindedly "big picture". She will help those in need only when it's convenient, nor will she go out of her way to seek justice on mortal wrong doers. Murders and thieves are simply not her department. That's life.
But she's not a killing machine; she's still a person. In her continued rebellion against her father, she has developed a pretense for disliking life's "frivolities"; refuses to drink to excess as it dulls the senses (but this port wine is awfully nice), she exhibits little pleasure in foods or physical comforts (although she secretly loves pastries and thick, soft blankets), and turns her nose up at anything that doesn't serve a practical purpose (even as she spends a bit too much time looking at a pretty dress or ornate music box at the bazaar stall). In a word, she's tsundre.
She also takes little genuine interest in sex, and prides herself on being chaste, although she is not a virgin. Being quite pretty, she would have had many admirers growing up. When she was 14, out of one part curiosity and one part boredom, she lost her virginity to a nice boy who was hopelessly in love with her (although she didn't return his feelings; I mean, he was cute and all but, meh). It was awkward and unfulfillinig, and she didn't feel very different afterwards. When she was older, she also had a brief affair with an instructor she admired, but it was messy, and he was married. There was also a confusing night with another girl, but that was a strict one-time-thing, and definitely not for her. In the end, her general attitude toward sex is, meh, unimpressed. Not for her, thanks.
Instead, she devoted her time toward physical training, molding her body into a tool. She excelled at martial arts, becoming one of the Seminary's top athletes. Not the best, but still pretty good. In combat, she favors the offensive, looking to end her opponents as quickly as possible, often focusing on a single target with extreme prejudice. She takes pride in her psychical abilities, and is quick to show off her biceps or hold contests of strength. Typical jock stuff, really. In the same token, she developed a real "locker room" sense of humor. She laughs at her own farts, makes dick jokes, and likes to put people in headlocks when she's feeling jovial.
Her humor may be crude, but she does have a knack for making friends. She's not one to talk much, and when first meeting her, she can seem like a very serious person (she also has a tendency to scowl, which can be intimidating). But she's also genuine and honest with people, guileless, and can quickly earn a person's trust. She's also pretty cute, too, and has a tendency to blush easily when complimented. So that helps.
And while it maybe a stereotype, she never focused on her studies. She's not stupid, exactly, but rather could never see the point in learning all that "useless stuff". She can be occasionally slow on the uptake, and often looses the thread of a conversation if it gets too complicated. If it seems relevant, she won't hesitate to ask people to explain something to her, but otherwise she'll just nod her head and pretend to understand what they're talking about. Not a big fan of fancy words, either.