@bd sorry to hear of your loss,
Re the g-mother, my mum had Alzheimer's - after my father died, she would look at their photos and ask where is he, after a few times of telling the truth and re-opening that wound we started telling a few gentle fibs, we also took his photos away - after a while the questions stopped and mostly we were happier.
A couple of interesting comments re dementia , 'they can't come to our world so we have to go to theirs' and 'the long goodbye'. I wish covid 19 was around about 5yrs years ago and I am sure my real mother would have as well.