How about the rest of you grow up and ignore her behavior around food. Stop letting her affect what you do and stop pandering to her. I know that sounds harsh, and I'm not trying to belittle the condition, but what you are all doing is not helping her, its going to be making her more ill and its not helping yourselves either. I'm sure you know, people die from anorexia and if you make her worse by pandering to her and that happens, how are you going to feel. I'm also sure you know, having had problems with food in the past, that what you're doing is not helping her.
Talk to the rest of your housemates, if she makes you feel uncomfortable, don't eat around her, take your food to your room and eat in private. In the meantime, speak to her about seeking help, contact her family to make sure they're aware and possibly speak to someone at uni. Its difficult because she is going to avoid anything to change or make her better, so the more people aware of her problems and looking out for her, the harder it is for her to run away from them.