Then there is my 98 y/o mother who has myasthenia gravis, eats whatever the hellll she wants to. Refuses the clot shots. Has been around oodles of people who have come down with Covid and is still kicking.
The rest of us have trouble keeping up with her.
Your mother has been blessed with anti-bodies for everything.
Some people have difficulty creating anti-bodies, others create them bigly. We are all different.