Eating Disorder Support Help

My boyfriend has bulimia, and deals with it fine when he's at college, but relapses when back at home for holidays and such. He doesn't have a good relationship with his family, there's zero trust between him and his mother, yet she's the one that controls the food in the house. He's vegetarian, which his family is rarely considerate of, and don't keep a lot of healthy, meat-free food around. I've suggested he talk with her, at least about what kind of groceries they buy, but it seems like communicating with her is impossible. I've suggested getting professional help to deal with his eating disorder, and this might happen. I don't know what else I can do to be supportive or what other approaches to take. Does anyone have any experience with eating disorders, dealing with them, helping people dealing with them, any suggestions? Please 😥