starts begging. What do I do?

Nifty is a plump doxie. She is very picky but eats alot, I DO NOT spoil my dogs. It seems that she only wants food...not affection. When ever we go outside with food, she starts jumping and crying. When the food is gone she starts looking for more! Nifty even steals food from my 2 year old brother. I am fed up with her greediness. What do I do about her?