Picky Eater?

So Ava doesn't like to eat bread. That's fine. Something I don't understand is how she can snub her little nose at a slice of carbohydrates, but then I will catch her over and over munching on crayons. She eats more crayons when I am not looking than carrots at dinner time. It's the neon waxy grin that gives it away. Sheesh!