My 13 year old daughter just told me her friend is cutting and I don't know what to do.

So my daughter just approached me after dinner and told me she discovered her friend at school has been cutting. My daughter noticed marks on her wrist and asked her what happened, her friend told her she fell over. While they were lining up for the bus, her friend tearfully confided that she has in fact been cutting and made my daughter swear not to tell anyone. My first instinct was that I need to tell her parents but I've never met them and don't know this child either, I wouldn't even know where to start with this conversation! I am trying to calm my daughter as she is very worried and frightened and doesn't know what to do. She suggested this girl speak to the counselor at school which I told her was a good idea but I'm not sure what else I can tell her and where does my responsibility lie? It was hard for her to break her promise of confidentiality and tell me so I want to give her the right advice. via /r/Parenting http://ift.tt/2sAAF3x