If she is a bit solid, look at portion size, because you can have a 100% healthy diet but too big portions and end up overweight. IMO any sort of "boobs" at 7 would indicate to me overweight. Normal weight 7 year olds do not have boobs.
My DD (8) would eat whatever I gave her, and always finish the plate. I now give her smaller helpings, but she can have more (within reason) if she asks. Also I don't encourage "pudding" fruit or otherwise unless she says still hungry. If she says she wants to eat something (esp at weekend) I ask if she is hungry. I don't generally agree to after school snacks but instead give them supper etc at 5pm if complaining hungry. Sometimes need snack at bedtime, sometimes not.
She does netball at school and swimming on sunday. We have a wii and I encourage her to play the justdance game which she loves, when the weather is better will do more outside, like bicycle, playing in garden.
I tell her we all need healthy food to keep us healthy and for energy, and that sweet treats give us energy too but our bodies don't need. And that if we eat too much sweet treats then we can get overweight.
re: the bullying, I'd say something like its extremely rude to comment on someone's shape, (and hope that you can help her slim out over the next year or so.)