My ex/best friend is self harming, is there nothing i can do?

Yes: If she is or was a close friend you should try to convince her to seek help. Counseling can help get to the root cause and overcome the compulsion. If she is young enough, you can contact her parents who could push her to get proper treatment. Whatever they do is not your responsibility. If you try to get them to seek help and they do not, then you are not to blame. Good luck to you and friend.