It's times like this that makes it hard to swallow some of our own principles. It's probably not the best time to remind people but Jesus taught that even this woman can have salvation.
"Forgive them, for they know not what they do."
I plead that God has mercy on her soul.
What you do is to tell your children the truth. MOST people are inherently good and would never hurt you. But the FEW evil ones PRETEND to be one of the GOOD ones and you can never be sure which is which, so keep safe and keep your guard up.