Fran
My late husband used to ask if I had seen his mother. I couldn't possibly explain that she had died many years ago. Used to tell the kind lies. Something like she can't come out in this heat/ cold, she's at the deaf club but is fine. It pacified him. I changed the subject as quickly as possible.
Of course it's a matter of choice how one deals with these heartbreaking situations. My personal aim was to try and keep my husband as content as possible in his dementia world