What kind of methods exist to help my friend who I believe has severe body dysmorphic disorder?

One of my good friends is fully convinced that she is horribly obese. However, she weighs between 100 and 110 lbs and is only 4’10’’. She constantly is talking about how huge she is and it really upsets me. Mostly because it causes me to worry about her psychological health but also partly because it makes me question my body size (I’m 5’3’’ and about 190lbs). She honestly believes she is bigger than me and is required to wear a size 14 dress. Recently she started a sort of binge and purge weight loss regiment. All she eats (if she does) is junk food, such as oeros, fig newtons, gushers, cheetos, etc., and then tells herself that she must work out for a minimum of two hours after her binge. Does anyone know of any methods or “tricks” so to speak that I can do to make her realize that she is at a perfectly healthy weight and that she looks wonderful the way she is?