Wow! My mum was obviously very lucky. My brother, who lived a few miles away, would pop in most weeks. Mum's neighbours on both sides visited at least once a fortnight and there were two old friends who made occasional visits. Her younger brother could always raise a smile - he was there perhaps once a month - her sister had further to travel, but managed it every month or two and one of her nieces turned up pretty much fortnightly. Oh yes, and one of my old school friends who was visiting her parents in the area tried to pop in to see Mum, too. As for me, 200 miles away, I went to see her on all my holidays from work and on Bank Holiday weekends and would visit twice a day when I was there.
If nobody's visiting your PWD regularly, I wonder if it's worth trying to find a student or somebody similar who would like to earn a bit of pocket money by going to visit and reporting back? I'd have gladly taken that on once a week for minimum wage when I was a student.