I agree that she is probably going through a growth spurt. If she is shoveling her food it could be a bad habit picked up from school, they have to rush through lunch so much my daughter who is 8 does the same thing at home. Just remind her about slowing down, or maybe give her her food a little at a time to get her to slow down.
As for sneaking surgar I think that's just a kid thing, they are always on the look out for the stuff!
Unless she has any major other symptoms I wouldn't take her specially to the doctor because of it, but maybe bring it up at her well child visit.