She said she could go a few days without eating. She does this because she's always felt fat. She's really not though. If anything she has a pooch on her stomach and thats all. I don't know any ways to help her? Or what I should tell her? Help please?

If someone doesn't want help, there may be no way to help her. You could direct her to somethingfishy.org.

There are usually organisations for eating disorders which have helplines, and at the very least there are certainly forums. Get in touch with those and they'll be able to give you advice. I was in a similar situation years ago when I was going out with someone who self-injures.