I think that you are wonderful and caring! As someone with an eating disorder myself, I can tell you that I would like it if I were treated with respect. I used to go to my boyfriend's family's for Sunday dinner (I don't anymore) and was barraged with comments...."That's all you're eating?" "Take more!" and so on. That's exactly what not to say, or how to behave.

Don't make a fuss over her, don't ask questions. Just be kind and treat her normally. be open and receptive, and let her come to you. She'll appreciate that.