Sorry to hear about this, My little brother started harming himself and he is alot younger, we had a school counsiler talk to him about his problems and it seemed to go very well for him, maybe something like that can help?

Do you normally go in her room? I mean would she automatcally asume you were snooping in her room if you confronted her?

I know when I was at school I was depressed to the point that I planned a way out and it terrifies me now to think about how close I was and to be honest I think all I needed was someone to talk to and someone who wouldn't judge me for anything I did, Luckily someone did help me and eventhough I still get like that now I know I can talk to my boyfriend about anything and even if hes just sitting there for a shoulder to cry on it makes things a whole lot better to get things out instead of keeping it all in letting it build up so maybe talking to someone else like an aunt or someone will help a bit I know you probably wouldn't judge her but I knew I couldn't talk to my parents because I was ashamed and I knew it would break their hearts knowing I was feeling like that.

I remember talking to a complete stranger on the net about everything before and I just felt so much better for someone knowing how I felt and not caring if they judged me or not because I didnt know them and would never meet them so I didnt really care it was just the fact that I could get it out of my system to someone

Im not a parent but Im 18 years old so maybe see this from her point of view?

You DO need to confront her some way alone and let her know that no one else needs to know and that you want to help her in anyway you can