My girlfriend cuts herself and tortures herself whenever she gets a stress attack. I don't want her

Its been year together nd we've known each other since first grade. I really love her. She's been sexually harassed. She has a low self esteem nd self confidence. People hurt her often nd well she never can rply back even. I wanna be there for her I cant bear her torturing herself like this whenever she gets upset or stressed out or we have a fight. She's real apologetic later and scared of herself.but its like an addiction yo her that soothes her. Idk I want her beautiful and happy. She really loves me and I love her back.i just wana fix this. Idk what to do please help us please.i don't wanna lose her
*plus I'm rude and cold with her whenever I get mad or upset with her that further effects her*
What to do?

I think she should go talk to someone about it, I am not a doctor but it sound like she has postdromatic stress disorder or ever depression.
All you can do is just say positive things to her and make shore nobody is bulling her.
She could be doing it for attention, as most teenages do.