My mother who has dementia thinks my father, who died 1 year ago, is having an affair bc he is never there. Are these fleeting thoughts?

My mother would get distraught that her imaginary husband was staying away for days at a time. I would tell her he was indeed home last night, because I saw him come home. It was late, Mom was already asleep, and he left again before Mom woke up. I'd also tell her I couldn't believe she hadn't heard him banging around getting ready for bed, etc. The more detail I gave, the better. It always calmed her fears.

They're not necessarily 'fleeting thoughts', no. Your mother can be stuck in a loop and insisting your father is having an affair for quite a long time when dementia is present. Try to distract her from this thought process, to the best of your ability, and watch some Teepa Snow videos on the subject of dementia. It's very difficult for us to deal with our mothers who have dementia and to constantly be trying to deflect their questions, and not so easy to just 'disregard' what they say. My mother is 95 next month with advanced dementia and she insists all of her dead siblings are 'just ignoring her' and have 'abandoned' her. I don't tell her that they're deceased, but having her think they've 'abandoned' her isn't much better than having her know they're dead! If I tell her they're dead, I'd have to repeat THAT story every day too, so it's a no win situation when dementia is present, let's face it. The subject is CONSTANTLY brought up, too, not something she talks about once in a while; it's a daily thing, and more than once a day, too.

If only it were so easy to 'just' do one or two simple things with our moms and have the whole ugly situation be take care of. "If only" huh?

Wishing you the best of luck dealing with such a painful situation. Sending you a hug and a prayer for peace.

Think of a brain with dementia as a destroyed brain. Disregard all the crazy thoughts.

Sorry for your loss. With dementia, things like this are really common. How do you respond to her? I would suggest not arguing about it, just try to tell her something vague like "Dad would never do that. He loves you.". I'm assuming you don't keep telling her that he has passed?