Is it okay for someone to be addicted to violence?

My friend had ADD and ADHD. She has anger issues, and goes to therapt everyday. I want to help but every time she gets mad and doesn’t talk to me anymore. We’ve almost disconnected.
She is a close friend to me becuse I help her out with school, but she always sees like shes always mad or has something angry on her mind.
She does have problems at home though, many of them. She always walks into class late. She listens to really scary music. And the only colors I have seen her wear since the first time I met her is black and red. She cuts herself and has the “Devils symbol” all over her things.
She used to be in a gang and fights alot, shes been to a mental hospital and juvi. Im really worried about my friend and I want her to be okay.