I understand that, but perhaps you could show her this from the New England Journal of Medicine, May 21, 2020.
“We know that wearing a mask outside health care facilities offers little, if any, protection from infection. Public health authorities define a significant exposure to Covid-19 as face-to-face contact within 6 feet with a patient with symptomatic Covid-19 that is sustained for at least a few minutes (and some say more than 10 minutes or even 30 minutes). The chance of catching Covid-19 from a passing interaction in a public space is therefore minimal. In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic.”
I get you. Not worth the risk nor the convincing. She is just as aware as everyone it might be worthless but who knows. Not much to ask right now.