The Nice Girl, Cuts?!?

Theres this girl in my school 13years old, and she is one of the nicest girls u will ever meet. She looks out for everyone, always there for u, she is just a loevly person. But yesterday I saw scars on her wrist, she had a long jumper on and it was a boiling day so she rolled up her sleeves, she faints if she is too warm. And she faints has panic attacks and fits for differnent reasons also. But I dont know why she cuts shes always happy, laughing, she is very pretty and quite wealthy. But this girls was Sexuall Harrased about 5months back, Everything is sorted now, and she always says 'Im not letting that pervert wreck my life' so I dont think it is that. Not many people know about this only her close friends. Im just a friend of hers but I found out cause she was crying in class before and she got took out, and then her friend told me. So i dont really think I can go up to her and ask her why she cuts, because im not that close. I dont know what to do? She always puts everyone before her, if its a decision weather to help someone else or her, she will go for the other person. So she wont get help on her oown? What can I do? And why is she doing this?