I guess it depends how much she eats, but probably. DS11 isn't a big eater. He was happy with the steak and didn't bother eating the side. The steak is on the small side, but I can't remember the actual weight. But with an app or soup, the steak, its side, and a dessert, that would probably be fine. They do have an adult steak that could be made without the butter and herbs probably. I don't know how big the adult steak is either.
Kid pics:
http://www.disneyfoodblog.com/2012/10/11/be-our-guest-restaurant-kids-menu-food-pictures/
Adult pics:
http://www.disneyfoodblog.com/2012/...w-of-be-our-guest-restaurant-in-disney-world/