Once I got done snickering at the contrary nature of children and other humans...

This made me want to find children's books about sparkly self-rescuing princesses. Or, failing that, to write one (with what time, of course). More seriously, this reminds me of the Pink Wars of my high school and college years. The opposite of forcing someone to do something is not to ban them from doing it.

(Another good reason to get the dresses from a thrift store is that when this phase passes they won't be tempted to say, "but you need to wear these clothes that cost so much!)