Have you seen the cuts? If there aren't any, she's just a "wanna-be" emo.
If she does cut her wrists, it's obviously not because it's "the emo thing to do". If you didn't already know, cutting is usally caused by depresion, when the person feels that physical pain can dull the emotional pain (Which is far worse). Ask her what is upseting her and help her through it. Be as optimistic as possible, but be very sympithetic.
Warning - while you were typing 2 new replies have been posted. You may wish to review your post. I have seen random scrathes and her arms, but she tries to hide it with bacelets and jackets and stuff.
If she openly admits she's cutting, why would she hide it? But do what I said above.