The Nice Girl, Cuts?!?

I'm not sure that this is something that you're going to be able to help on your own. She sounds like she's going through a lot, emotionally and otherwise. I think the best thing that you can do is sit down with some one like your parents or an older person that you trust and explain it to them. They will know what the best thing to do is. If she's abusing her self as you say, and you really care for her, tell someone right away that can help her before it goes too far.