It's the distinction between "natural" fun and "artificial" fun. Sure, her mother might've dressed her like that, but it's still pretty natural fun.
I wouldn't blink an eye at kids running around naked at a swimming pool, but I'd be extremely worried if I saw a little girl in a miniskirt at the shops.
... And a little girl in a thong, mini-bra-thing and feathers at the shops, or walking in the street? I mean
come on. If her mom dressed her like that, it's just as artificial as the dance routine.
I... just ugh. Little girls should play in the dirt with their goddamned dump trucks, kick soccerballs, and plant crops. Tricycles. Forts. Dolls, if they're so inclined. Dance for the sake of dancing, run around stark nekkid on occasion, whatever. But not this sexualized crap in front of a big audience. I think young women need a chance to just
be themselves before starting on the whole appearance-altering fuckfest that adult women get thrown into. They need to learn who they are, so that when the world starts asking them to pretend they're something they aren't they can know what's happening. They're all right if they're a bit chubby or skinny, they're all right if they'd rather play with swords than dolls, they're all right if they're lonely, they're all right if there's too many people around. You need a sense of self before you can put on a mask without losing that self, and I think too many women nowadays lose themselves to a mask due to starting shit like this too soon in life.
Before you learn to be perfect, you should learn to be imperfect. Life will be gentler, that way.