My grandmother has dementia and I've experienced much of this and it is indeed very heartbreaking.... often when she asks the same question I'll try different answers to see which one elicits the best response. Anything that makes her laugh becomes my default answer to that question. It's like a test you can't fail because you get to do it all again 30 seconds later.
It's tough stuff and we made the decision not to tell my grandmother that her own daughter (my aunt) had died of cancer back in 2017. My father (her brother) and I had a huge row about it because he believed you couldn't keep the death of a child from a parent - I disagreed and talked him round and so for the last six years, flowers have been arriving on her birthday from her daughter who is always 'off on holiday' when she asks. She doesn't need to know and if she did know, she'd only remember there was something terrible she didn't know yet.
Beautiful article. Looks like I'm late to the party, but it's a great party to come to. :o)