IT'S A GIRL!!!
I took her to the vet today. He said she looks like she's in good shape - no mites, no fleas that he can see, all signs normal. She's too young for the feline leukemia test, so I have to take her back in two weeks. In the meantime, I can start mixing solid food with her formula, giving her wormer once a week and looking very, VERY forward to the day she's ready to start using the litterbox.
She's a chatty one. She didn't shut up pretty much the entire time we were at the vet's office. Fortunately, everyone thought she was just adorable and forgave the running commentary.