<human>: This is probably a really basic problem but I am stuck for answers and I don't really know what approach would be best.

I've known this one girl for like 2 years and we weren't really close until about 8 or 9 months ago but while we were just distant friends everyone always agreed that she was really really hot. When I started hanging out with her I saw it even more, she'd have guys falling at her feet and creeps buying her drinks all night and sending her nudes.  Even I ended up falling for her when she made me a cake on my birthday, cos usually girls that get so much attention don't need to be really sweet as well.

She has been a vegan for about 18 months which never really bothered me as she takes supplements and stuff to be healthy but recently I've been alarmed at her talking about dieting and stuff. She is definitely not overweight, but seems convinced she is. Although she is ridiculously short (4'11") she weighs way less than me and I'm underweight slightly myself. 

We were at a party in her house last night and she wouldn't eat anything and said that she fasts every two days. I really don't know what to do as I am worried about her health both physically and mentally. Obviously complimenting her or telling her she's gorgeous will have little effect as she gets this all the time anyway and I was just wondering what I should do?

Can you condense the text into a few key points?
<bot>: friend is using alarming diets to lose weight. already the most beautiful girl I know. what to do to help her self-esteem/body image?