answer:One: wearing colors you don’t like and listening to music you don’t like don’t mean anything. Two: Everything else brings up the red flags. Yes, of course it’s a bad thing for someone to be habitually violent. It kind of makes it hard to have lasting and reciprocal relationships. It sounds to me like you’re more asking how to help your friend. I can’t say I know besides just trying to communicate and talk about her problems, or get her someone to talk to, like a counselor. She might just need to change her living arrangement, which i know can be hard in high school (I’m assuming you’re in high school, from the sound of it).