nrb80, your post was excellent. My family's situation is a bit different in that it is my (welfare queen) sister who, having been given money for a long *long* *long* time (we all were, as gifts over the years, but her asking went far beyond that). My father died on July 9 (a Monday) last year around 8:00 am. Two days later, almost to the hour, my sister approached my mother, who suffers from short-term memory loss, and asked her for $1,000. I was out doing a much too long walk and having difficulty struggling home. My niece, my other sister's daughter, overheard the request and immediately texted her mother at her home around the corner that someone--her or one of our brothers--better get there immediately. They all did.
When I finally staggered home and drank enough water to recover--I was so out of it I must have disrupted a "discussion" without knowing it--I was told they wanted to go to lunch and would wait while I showered. I came out to a living room where everyone was sitting around and had obviously been talking about a delicate matter. It was then I learned what was going on.
My mother wanted to give her the money. My brother, who had for a while been handling all their finances with their blessing--was explaining to Mom that yes, it was her money, that she could do with it what she wanted but that he had promised Dad that he would take care of her and that meant seeing she did not run out of money.
It was a painful, deeply intimate family discussion with, as you can imagine, all attendant emotion. It did not end well. And the question about where to take over, where to intervene and where to let the parent make all the choices never really did get resolved though decisions were taken. But it wasn't really solved. And I don't know that it could be. Sad all around. For you too, OP.