<human>: Condense the text into a few key points

I've been with my girlfriend (F17) a little over 2 months. This might not seem like a very long time, but it has been the best two months of my life. It isn't all fun times though, as she can have really extreme mood swings. 
When I first got with her, I was head over heels for here. I probably still am, but I'm beginning to suspect she may be depressed. Her previous boyfriends have messed her up really bad. She has nightmares of being raped and constantly suffers from lack of confidence and hope.
 We have weathered everything together and I try my absolute best to be there for her when she feels at her lowest. Despite this nothing seems to get any better. Last night she told me she wanted to start starving herself to become thinner. She is already thin, not scrawny... just the right size and I'm 100% attracted to her. 
I told her I wouldn't support her if she did that. I also offered to help her lose weight if that was the problem but she just thinks that starving herself would be quicker and easier. 
She claims to know what she is doing, even though she's been in hospital before for not eating enough. I'm at my wits end and all I want to do is help. I'm not perfect, I don't know the answer to help her this time and I'm really worried the worst might happen. What do I do?
<bot>: My gf is asking me if she can start starving herself to become thinner. She has been in hospital for this before and I'm really at a loss with what to do/say?