The girls/women thing is easy. If they're children, girls is fine as a girl is a female child. Otherwise women. Ladies, well, I'd stick to women, because although nowadays many young women don't seem to mind the term, if you call an unreconstructed second wave feminist like me a lady, you'd be wrong, because I'm not.
Regarding the story if you had made it up it wouldn't be sexist, as far as I'm concerned, but you would have been a bit of an idiot to do so.