It seems unruly, maybe rude and crude, but it did not sound sexualized.
It would not seem wrong to ask how old do they have to before wearing more clothes in front of each other, it may offend her slightly.
But I guess it gets down to people pleasing. Do you mind offending her? Is it that important for her to be happy with you?
I guess I have embraced my not so much people pleasing side. I would just ask her in a laughing way. Like how much pubic hair does a kid need before they have to go around with clothes on, in a snarky way
It seems to violate your conscience. That is the big thing.
And if you share your opinion and she ignores it, then what? No evidence of abuse. It is like wearing a bathing suit.
I personally would find it weird and tell the kid to put some damn clothes on. Little heathens....