Not sure what eating disorder it is

My house-mate shared with me that she has been struggling with food issues, but I'm not sure what it is so I'm not sure how to help her. She has a lot of food allergies and abuses some of them (eating too much processed sugar, too much fruits & veggies) so that she can have diarrhea to rid her body of food. She thinks a good day is when she gets sick (diarrhea) first thing in the morning, and a bad day includes when she eats a snack when she gets home from work. I do most of the cooking, and cook pretty healthy (and follow the do's & don'ts of her allergies - dairy, wheat). She desperately wants to lose weight and look differently, but of course it's for the wrong reasons and she's going about it the wrong way. I really want to help her, but I'm having a hard time finding info to share with her on-line because she isn't anorexic or a typical bulemic. Please share some wisdom! Thank you!