Bex is intelligent but doesn't prioritize academic learning -- in fact, she aggressively rebels against it for various personal reasons and I think if that were more important to her she'd choose to rebel against other things instead. So no to Ravenclaw.
She lacks literally any of the values of Slytherin -- power beyond sense of self isn't important to her, she's not goal-oriented at the moment, and she's a "kick problems in the face" person rather than someone who prefers cunning and cleverness. She's far too straightforward to fit in with Slytherin.
Hufflepuff might be a decent place for Bex, but I think she'd rub other students the wrong way with her attitude. She's not unkind, but Bex has a lot of walls up and can be needlessly aggressive.
Bex belongs with Gryffindor, but she doesn't think she does. She identifies with their more aggressive traits, and will insist that hell yeah, she's not afraid of anything -- she's reckless, she's wild, she's got a disregard for rules and thinks she knows better and can make all her own choices on her own. But give her a quiet moment and she'll say that she doesn't think she fits in here at all, because she always feels afraid, always feels like a coward. She'll feel like she doesn't belong with the stereotypical hero types.
But at heart, past all of her trauma and troubles, she's got nobility and strength of will. There's a real bravery in her but she doesn't see it, and I think that when push comes to shove, Bex values inner strength and courage above anything else. It's not just who she is at heart, it's who she aspires to be.