My DM also often said that she'd rather die before going the way of her DM (my DGM) who developed Alzheimers (shortly before her death in 1991 she would ask my Aunt when visiting if she "made it through the bombs alright").
Sadly she developed an aggressive form of vascular dementia and went from compus mentus to catatonic in about 6 months. Eventually she had a fall and broke her hip and no one realised for 3 days as she had no reactions. From there (over 3 months) it was hospital, hip replacement, pneumonia (obviously) "recovery", waiting for discharge to community, death. Not easy to write, less easy to see and a horror to keep.
It would have been her birthday last Sunday, something to keep.