Worried about a friends health condition. Any advice?

My friend has just been diagnosed as anorexic. She can’t eat much at all without puking it all up. She hardly touches a thing to eat all day, not even fruit. She doesn’t even drink much water, and I’m very worried about her.
She isn’t willing to talk about it and often has to go home from school in the middle of the day due to feeling ill or faint. The teachers all try to persuade her to eat after finding out about her medical condition, but they’re not able to do much. Her parents dn’t want to force feed her as they say all she does is barf it up again.
I was hoping for some advice as to how to handle this situation as she is my class mate at school and I feel I can help her, only I don’ know how.
Thank you.