While Sally is usually girl's name, the question never states that. So Sally could be actually a boy and in that case Sally would have two sisters.

Fair enough.

You’ll get some eye rolls from people when you bring that up for Sally.

But there are several names that used to be considered male but are now female, like Leslie and Marion. I don’t think I’ve ever met a man name Marion, but you still occasionally run into a Leslie.

It would be interesting to start using Leslie for this little logic puzzle and see how that affects people’s answers.