Do you think my little sister might be suffering from a type of EDNOS ?

So my sister is ten and recently for the past three or four months she's been constantly saying things like "all my friends say I'm skinny" as if she's thinking things over. And once or twice she's complained about the "fatness" of her legs. I never really gave it much thought until about this past week when ever she eats anything she's been sick after taking a mouthful and she starts crying. Yesterday and today she's been refusing to eat anything but on friday she eat fine sweets and everything. What's going on? Do you think she's a risk of developing an eating disorder? How can I try to talk to her?