Well first, I dink you guys are having supper too early(6). Second, it may be because of the chocolate milk and veggie's she's having at supper. I'm not saying you shouldn't feed her those things, but chocolate milk and veggie's tends to fill your stomach up very quick, but doesn't last very long. Maybe you should try giving her meat for supper first and veggies and milk last before desert. That way, after she's done eating her meat, if she's still hungry, you can give her one more plate of meat with veggies and milk.

Try giving her a glass of regular milk before she brushes her teeth? lol

Hope it helps