Two things could be causing your daughter's enlarging belly. One, if she is a compelte vegetarian, she might not be as careful about getting the protein that she needs. You've seen children with bloated bellies because they can't get enough protein. If you are positive that she is getting the required nutrition, then it might be that as she approaches puberty her belly is larger. If this is the situation, it's temporary and will resolve itself as she matures.