Pretty messed up

today i found another cut on her wrist, under one of her favorite bracelets. Did she thought i wouldn't see it? I told her that if she was't able to stop by herself i'd have to tell her mother, to take her to a psychologist. She told me that a reason for not doing that is that she's my best friend, but the truth is that that's just another reason to DO it. i cried when i saw the cut. I don't want her to get hurt, and since i've never done it, i don't know how she's feeling, and i don't know what to tell her. i don't know how to comfort her. i don't know if i should tell her that everything will be alright. What will be alright? she doesn't wanna tell me what's wrong. I honestly have ran out of ideas of what to do.