There’s nothing wrong with a little child asking a question like that but, when they do, I think a parent should explain two things: that they should not approach or talk to strangers and that it’s rude to talk about someone’s looks in front of them. (It’s not particularly nice to do so behind their backs but that might be expecting too much.)

I think, in the incident you related, the woman gave a charming answer. She signaled that she knew you meant no harm, yet didn’t reward your behavior by giving you a straight answer. I like her.