I raised my kids to not care diddley-squat about stupid people and their mean putdowns and 'making fun of' - we have a handicapped 'child' and they all three learned at an early age just how cruel and nasty people can be - adults as well as children...
And as hard as it is to face - some people will never 'get it', and they get a certain pleasure out of being mean and bad and nasty - I taught Angie (the one who is still here with us) to tell them "God is watching you" - of course, if they are atheist, they don't care (LOL)
Just assume that this woman is a nitwit and go from there - bless her heart......