[Rinni]

It might be hard, and there might be tension. But confront her, sit her down. Let her know you're there for her. Explain your worries, back it up with observation. Be careful not to be accusatory; put it gently. Explain how worried you are.

If you can get in touch with her parents, her family, or those around her....do so if she won't respond to you. They may not know she's hurting. Give them the chat logs if need be, and explain the situation.