This is a tricky one. Self injury does not necessarily mean that your friend is suicidal, for starters. Do you know her parents? Are you able to talk to an adult, perhaps a guidance counselor? The best thing that you can do is be there for her. Be supportive, listen to her. Don’t try to pry information out of her, or scold her for what she is doing… odds are she is not proud, in fact, she is probably ashamed. For some people, self injury has an addictive quality. It is a coping mechanism, a way to deal with depression or other emotional pain. Strange as it may sound, cutting can be soothing to a person who has a tendency to self injure. Your friend should talk to a doctor or a therapist, and hopefully she has a supportive family that can help her seek those resources.