Daughter problems,please help!!!?

My 11 year old daughter has been acting different. Her math and science grades have gone way down. She has been giving attitude and acting depressed. She says every time I ask her if she's okay she says she's fine. I know somethings up but she won't say anything. She used to be so happy and bubbly, always talking, always laughing. Since school started, she's been saying less and less, not laughing, not smiling. One day I got a call from the counselor saying something about her wanting to die. When I asked her about it,she said this, "You know when somebody says I'd rather die than be here? That's what I meant." And now she has a strange obsession with Johnny Depp! All she talks about is him, all she thinks about is him, and that's the only time she will smile or even talk. And now she's saying her social studies/homeroom thinks she cuts herself because both Thursday and Friday 2 weeks ago he asked to see her wrists. She always looks sad and always looks down nowadays. I'm thinking the reason is because I'm newly divorced and I have a new boyfriend, but that's not the reason because she's been like this since August and I met my boyfriend back in November. I also noticed that on her search bar on our family computer she's been looking up Am I Depressed quizzes. Is this serious depression or just a case of the serious blues that can be easily cured?