She sounds like a real piece of work. If she can’t make minor sacrifices to her personal entertainment schedule for the sake of her children’s welfare now, good luck with motherhood lady. The Spanish Flu pandemic babies ended being 2-3x more likely to develop Parkinson’s later in life. God forbid that this coronavirus cause the delayed onset of serious health issues in our children, but if it does I’d be pretty resentful if I were her child that I had to deal with lifelong health issues because mama couldn’t stop wandering around a contaminated grocery store for idle entertainment.

Your plan to blame it on your doctor’s orders is the most diplomatic route, although even that might not be well-received depending on how obstinate they are. I did that with my anti-vaxx friend - I literally asked three pediatricians and they all told me not to bring my newborn around the anti-vaxx house, told my friend as politely and delicately as possible that the doctors advised me that people need to be vaccinated to see the newborn even my parents, and she responded with a fit of histrionics saying I made her cry.