I think my friend has an eating disorder?

Ok so my friend (lets call her Kelly) anytime and anywhere she can get food she will take it. Now she is 13 and we all know about our periods and all those cravings, but this has happened even in 5th grade. So i was with her at the lake and she brought $20. Then there was a cafe sort of concession stand. She told me to follow her im like ok. She got a cheeseburger with fries and a thing of Oreos and sugerd ice tea. She is erm wide. I don't think it is her fault, it is her moms. Her mom doesn't care at all. Like if i call her i will always hear munching and a rustle of a bag. I went over there for a sleepover, all she wanted to do was eat. We watched tv she said brb then she came back with a bag of popcorn with *extra butter*. Then before we went to bed she brought up a box of dough-nuts. In the morning (she has a walk in pantry) and she made roman noodles. Then her mom came back with McDonald's for breakfast. She got everyone those huge breakfast platters. Also when she comes to my house, every hour she is like "Can we have a snack?" I don't like having her over my house because my mom says i eat everything and when i try to tell her it was my friend, she says "Don't blame everything on your friends." When we went to the lake she finally believed me. What do I do?