My girlfriend suffering from suspected borderline personality disorder, self harming, binge eating?

Aww, sounds like you really care for her. That's sweet. I guess what you have to do is, is tell her how concerned you are, that you think she needs counselling, professional help. Then you can support her, but she has be helping herself too. You have to tell her too, that her mother is not a good influence in her life, and she deserves better people in her life like you :)