This is just my own personal experience. I had a friend who wanted to come to my house, or Shelly's house, or whoever's house, and then she wanted to eat. I stopped inviting her over because she'd eat everything in the house, and my parents would get mad at me for letting her. But, I didn't know what else to do.
My 17 yr old has a friend who went through a huge eating spurt. (but she was older and realized the effects it had) She came over to sleep over, and she drank SIX cokes in one night!! Plus, a box of cupcakes that I bought for them.. so, I didn't care. I just assumed they'd eat one or two.
I didn't worry that her mom would be mad at me. But, if my own daughter ate all of that in one night, I'd be pretty upset with her. I felt kindof bad though, like I enabled it or something.
I am not overly concerned with what my child eats. I buy and cook healthy foods, so whatever snacks she has is OK with me. But, I don't want her going around finding as much as she can get. I also don't want her going into other people's homes and asking for food.. or even hinting for food.
I don't have any good ideas for you though. But, I would also be worried about her weight. We all know we shouldn't focus on weight... but, in reality we do. As moms we can't bear to think that life will be difficult for our kids. And, being overweight is difficult.
Almost ALL kids do go through that chubby age in about 4th-6th grade. It's pretty typical, and doesn't always mean they will have a lifelong struggle. Some kids just grow out before they grow up.