Hi...I know this is old..but I wanted to get my two cents in as I disagree with what was posted.
Obviously everyone is different, but I used to be a cutter in high school. I was NOT seeking attention. In fact I only ever told my therapist after going to her for over a year. I was abused as a child, and would be physically hit or hurt when I cried or became angry as a kid. As an adolescent, I had learned to hide my emotions, and for me feeling the physical pain provided a type of release that was easier to deal with than anger, fear, sadness, etc.
Luckily my mom caught me and put me in therapy. I am now in my thirties and STILL in therapy. I no longer cut myself, but I have to admit sometimes when faced with severe emotional pain it crosses my mind. I am not CRAZY or bad news. I am capable of having a loving relationship, though of course I do have some emotional, and physical, scars from my past.
That said...I agree that it is NOT your fault she is cutting, and NOT your obligation to fix her. I also think it is wrong of her to throw this in your face and put the blame on you. That said, she clearly needs help, but is not CRAZY or a horrible undatable person. I would wait until she is calm, and then tell her she needs to seek professional help. If she is unwilling and you must leave the relationship do not feel guilty, but do maybe try to talk to her friends/family and let them know she needs to talk to professional about her behavior.
I feel for her. It is horrible to suffer such emotional pain that the only thing that feels better is inflicting physical harm on yourself