Unfortunately it's quite common for elderly people who badly need help to refuse to have carers coming in. And unless they have been officially deemed to lack capacity, there is little anyone can do. But it's very hard on anyone who just has to stand by, helping as they can, or are able to, and wait for the almost inevitable crisis. My OH had an old aunt who wouldn't have any of the care we arranged - everyone was 'too loud' or 'too common' (!) etc. and they were all sent packing. Another factor was that although she had plenty of money she was terribly tight and just didn't want to pay.
But she needed help so badly and we lived a 2 hour drive away. She was relying a lot on elderly neighbours, many of whom were themselves pretty decrepit - the poor things would phone me wailing, 'We can't cope any more!' In the end OH managed to get her into a care home, but boy, it was a monumental struggle, and she only gave in when she was no longer even able to get herself to the loo. OH who has infinite patience finally spent an entire day with her, when she was refusing all day to go to the care home place he'd arranged. She just kept saying, 'what am I going to do?' and he would say, 'you know what you've got to do.' At about 9 pm, and up to here, he said, 'Sorry, but I've got to go now,' and only then did she give in.
It's rather different, but we have an elderly neighbour who we found out by chance was spending an absolute fortune on a lottery scam - convinced that this £1m 'win' was going to appear if she just kept shelling out for 'tax'. She didn't have dementia - just terribly naive and trusting when someone purporting to work for a high street bank phoned to tell her she had 'won' this prize. Friends kept telling me I 'must' do something, I 'must' tell the police, but in reality there was nothing we could do - she simply would not believe it was a scam, would not let us report it and begged us not to tell anyone, and the law takes the view that if they have capacity people are free to waste their money as they wish.
In the end her children managed to divert her post and get a phone that only allows trusted callers, but the woman in question still had a husband who understood the problem and was able to cooperate. But by then we were told that about £100k had gone in 'tax' to these evil scamsters.