How to help a friend who self-mutilates?

I have a friend who self mutilates herself.. what can I do to make her to stop?
and I dont want to get her mad..

Talk to her about it and ask her why. Be nice about it. From there, if you see it becoming worse tell someone that could help her. She might be mad at first, but if you are trying to help its worth it.

As dancer003 said, talk to her, try and understand why is is doing it. If the cuts are something you really worry about, get her into therapy or some sort of rehab. Either one can work of a person. If it ishome issues, try letting her stay over a few nights and really finding out what is wrong. If you can sit beside her, show her that your there for her, she will open up, and tell you, and hopefully ask you for help.

A warning of advice, be prepaired for anything, a lot of bad events could of happened to her, and if she says, don't cry, it will only make her feel worse in her time of depression.