My late wife's aunt has the same problem you describe, Red. She can tell you what she did forty years ago, perhaps, but can't remember what she had for lunch.She is not in a retirement home where she receives three well balanced meals a day, receives her medication on schedule and looks 100% better than the day she arrived six months ago.
Folks like this cannot manage on thier own. It is dangerous for them to try.
I was told by the resident doctor when I visited last month (the home is 1000 miles away from where I live), that of the 78 residents in the home, all of them who are still mobil hope someday to go home. It's almost instinctive, I guess. The home (if it is a good one) is the absolute best place for them however, to protect them form themselves.
I think Sorcha's suggestion for a lead in to the telephone conversation is excellent.
DougR