My girlfriend cuts herself

first off let me say that i love my girlfriend 100% and thers nothing i wouldnt do for her. my girlfriend has a few problems that i seem to care more about than she does. right now im only focusing on this one though. im going to go ahead and say im a little too over protective but still whatever other people say im not giving up. her previous boy friend died in a car crash that a jealous x caused. she was in the car when the crash happened. ever scince that happened she has been cutting herself. at first she just said her cat scratched her but after a while i got suspicious. fortunatly before i had the oportunity to screw things up by asking her about it she told me. it took me 2 months to get her to explain why and i havent demanded she stop or anything like that. she doesnt think its a big deal and cant understand why im so determined about it. ive been as gentle as i can be without her thinking i condone it. im not giving up. i refuse to give up. i wont let anything happen to her and im not going to let anyone hurt her. i guess thats partialy why its so hard for me because i cant protect her from herself… i love her and it kills me that shes in pain. self inflicted or not. please dont tell me to get an adult involved because trust me if i see any sign that shes in danger of hurting herself to badly thats the first thing im doing...