Afraid my friend has anorexia...?

This is horrible.. It sounds like your friend really does need help and if the teachers aren't doing anything about it that doesn't even sound right. Maybe you could talk to your friend about whats going on with her and if not maybe you could talk to a teacher and ask them why the hell they aren't doing anything to help her... and another thing you could do it just talk to her parents. They might want to know whats going on, thats if they haven't already noticed..