I had the same problem with a 92 year old step cousin.She was very compos mentis , but manipulative and incredibly nasty at times. She has a son who lives abroad and perked up no end when he arrived so yes lonliness was a big factor. Myself,unwell grandson of 50 and several of her neighbours looked after her between us through lockdown, but she got increasingly demanding and unreasonable,calling neighbours or me at all hours ( once to prune a plant that was annoying her she- told me it was 'very urgent'! )I got worn out and my health deteriorated so I took a huge step back.The neighbours were trying to do the same,it was left mainly to the grandson who has major heart trouble,so she did end up paying carers and was just as unpleasant with them mainly cos she had to pay for the service! Eventually after a few falls and broken bones- she still expected neighbours and close family to rally round her in the middle of the night- she begged to go into a home,but as soon as she was in a good local one,wanted to come back home as she couldn't order people about and put her demands for instant attention and jobs to be done on the staff there.When I last went to see her,she had hit one of the staff 5 minutes before then told me to bu**er off in no uncertain terms.
So please harden your hearts ,if someone has POA and I assume they are relatives,leave it to them.I hope I keep my cousins behaviour in my mind and never turn into her!