Thank you Jessie and Diaminohexanoate!
I will try to talk to her about this. Like you said, we are not really close friends. But I know she was a really nice girl before, and I just wish I would knew more about her and her past. (It seems like she's struggling about her past.)
Today I saw her wrote a letter to her friends saying, "When I saw the blood comming out, I finally realize all these things won't really matter anymore." She is still doing the same thing I guess.
I will convince her to talk to someone she trust, and should I ask her about her past and what she's so sad about?
And don't worry about me,
I know she's in a bad mood, that's why she blame it's my fault. Sigh, no matter what happened, I know I will never never hurt myself or others!
Thanks again for the suggestions!