What happens to the soul of somebody with late stage dementia but is still physically alive?

I know there’s no true and proven answer to this but I’ve just generally been curious.

My grandad passed away just over seven years ago, and since his passing I’ve occasionally dreamt about him which recently, the more I read posts on this and similar subreddits, I’ve come to believe that these are visitation dreams.

Since my grandad’s passing, my grandma’s mental health has severely deteriorated and she’s in late stage dementia, to a point her character most of the time now is nothing like how my grandma used to be and is barely even a shadow of her former self.

One night last year, I had this dream where I’d woken up in my grandma and grandad’s living room sat up on the floor in a position I used to sit in there. My grandad was sat in his chair having a general chat with me, my grandma was in the kitchen cooking and cleaning but popping her head into the room to join the conversation and then get back to what she was doing.

The dream was so comforting, as it felt like life about ten years ago. It was more as if the last ten years of my life had all just been some awful dream and I woke back up in 2014 or something. Grandad cancer free and healthy and my grandma without dementia. Just life being normal.

I wondered from there if my grandma’s soul had potentially left her already, was reunited with my grandad’s and that dream was a visitation dream from the both of them?

I’ve tried to go back to that moment in my dreams so many times as I’ve never felt comfort like it before, but just haven’t been able to.

I’m just wondering what typically does happen to a soul of a dementia patient?