Something from the past, no doubt, that has a strong past-experience charge for her that got triggered by some aspect of it. My guess is it’s any time she has told her child about something, and they seem to her to be doing something like the situation she has a charge about. Not knowing her nor having seen more than what you wrote about it, I couldn’t say, but it’s a pretty common sort of thing for parents to have a hang-up about. It’s often ancestral and passed down from generation to generation.