I hated this prompt because I felt certain they meant 'Quirk' as in BNHA, but for the life of me I just couldn't come up with one for her that I liked. Which is stupid because quirks can almost literally be anything in the world, but I guess I'll chalk that up to a general lack of creativity on my part lately.
At any rate, I guess one of the bigger quirks in Vin's personality is that she thinks she's really good at holding her liquor, but in reality, she's a featherweight drunk. And she's obnoxious. She gets loud and stupid after the equivalent of a beer but she'll deny it til the day she dies.