Seriously, this is affecting her enough that she grimaces when her suspicions are confirmed, and her first action is to take us aside to talk to us.
It is probable that she knows the lichbomb. It is plausible that she has been witchbombed. It is certain that she understands, viscerally and completely, that being meguca is suffering. Whatever memories she has, they're strong enough that they still affect her twenty-ish years later.
No corny puns here. No theatrics. Her primary motivation right now, strong enough that she was willing to confront us directly about being magical girls, is that she is concerned for the safety of her daughter and her daughter's friends. And that means that helping her and reassuring her is our primary goal in this conversation.
Even beyond that... what do we want out of this? We've wanted an adult sympathizer forever. It would make things so much easier. We have one here for us... as long as we remain on friendly terms with her and can convince her that we are A Force For Good. We want her protective instincts behind us rather than in front of us. So being compassionate and reassuring is, beyond being the right thing to do, is our best play from a rational perspective.