i dunno what 2 do...

hey everyone.. i need some advice..

i'm very sure my sister is anorexic.. she has a ton of symptoms.
when she eats it's very small and it excludes carbs and things like that.. ex. if she eats a hamburger she won't have a bun.. stuff like that. she is extremly skinny and has lost a ton of weight.. she is 17 years old, about 5' and weighs about 90 or less. she will also feed other people a lot and will get very upset if i don't eat. and the other thing is she exercises a TON she is constantly running and stuff everyday, and plays sports that cause her to lose lots of calories.
I've tried to tell my mom but everytime she denys it and now i don't know what else to do, and if i talk to her about it she blows me off... i'm so confused and scared.. i love her so much and i don't know how to help..'

advice??

Does she think she is anorexic? What she say when you ask her why she is eating like she is?

no she doesn't think she is anoerxic.. not that she admits at least.
and when i question what she eats she claims she doesn't like the food, which she did like her whole life till she started showing signs of anerxia