Mi oldest chihuahua looks to skinny. When she's laying down and rolls in a ball to sleep like any other dog, you can see every bone in her spine popping up. I see her eat here and there, but it's hard to keep track of how much she actually eats, because I have three chihuahuas. She is very active and plays a lot. Her ribs don't really show, and the vet says she's fine, but all of our chihuahua owner friends tell us she's too skinny. Please help