Around here, even to Sunday church, young women go from ballet flats to little kitten heels (barely a heal, little more than heal on mans dress shoes) by twelve or thirteen. By almost sixteen, definitely be a late bloomer. I agree real heels on young teens is not appropriate, but on nearly a sixteen year old, more surprised just starting to see a small heel now.
I get the feeling, for official events, they think they need to dress the girls really girly and traditional which some times comes off a bit young. In casual pics we get the teen Elisabeth in more clothes you'd expect a teen her age. This dress is lovely, and showing even in public events, they are allowing more growth.