Replying to my post earlier: LO doesn’t have dementia, she had a brain aneurysm. So, now has cognitive impairment.

When my mother was in a nursing home there were several residents who were surprisingly young, one in his thirties. Sometimes life deals a hand of severe medical complexity that requires care beyond what can reasonably be accomplished in a home setting, even at younger ages. The residents we got know truly had to learn to make the best of it, had their rooms set up for hobbies, and spent time with staff more as friends. I wish you well in navigating this

My mum had cognitive impairment following a brain hemorrhage, 13 years ago. Now she has vascular dementia.

For a few years following the stroke, Mum's cognitive abilities improved. If she had been allowed to learn to become more independent again, during that time, I believe that her cognitive decline could have been slowed down.

I hope that your sister's condition is capable of improving.

This is an aneurysm without any dissection. But it still is causing problems?
I am not sure I understand, but it must be putting some pressure somewhere.
My brother, in his ALF, was for the most part in much better mental condition than others. He still made the best of it, and it was in fact great with so many of the elders there. He, another woman, and a man with a seizure disorder were really in quite good shape.

This is a matter of adjustment.
So often in age (I assure you at 81) things are less than perfect. We expect happiness of life, but when you think of it, life is SELDOM about "happiness" at any age. We live, we struggle, we celebrate, we die.

As conservator you are taking on responsibility that is not yours. You didn't cause any of this and you cannot fix it. You will do the best you can with what gifts you have. There's no nirvana on this side of the shade. Try not to trip into the future overmuch. Take things a day at a time. You cannot know where any of this will go.