Eating Disorder Help

I have a problem with my weight but i know dieting won't help. My cousin on the other hand believes it does work, and won't even eat some days and I'm worried for her. She only weighs 90 something pounds but she still thinks she's fat. I've tried talking to her about it before but every time i mention eating she shuts down. I don't know what to do that will help her and not make her hate me. She's been my best friend since i was born and i don't want to lose that. I believe that she may have anorexia but she refuses to talk about it seriously. The only time I've ever got her to talk about it she admitted that when she was little her little sister and her father teased her about her weight. She wasn't even 7 and barely weighed 50 pounds. Yet still her father called her fatty and told her that he wouldn't have a fat daughter. This scarred her and helped cause her eating problem now days. I was hoping that some of you could give me some advice on helping her. Please no hating.