OK - I'm a US resident (not citizen) and many moons ago contemplated doing this with my mother. I was going to use pipop1's suggested mode of travel (cruise ship). Because of the financial issues of healthcare it really was a non-starter unfortunately. But what I did do, and made my life and Mummy's much easier in a practical sense was finding an extra-care facility with a really good and reliable on-site care manager who would basically do all the things I wasn't available to do. All the everyday things, such as food, cleaning, clothing, personal care, plus necessary medical appointments and the like.
I fully understand the panic engendered by having elderly parents 3000 miles away, and in the OP's case my understanding is that her visa status is such that she will not be able to return to the UK if there are problems (which I didn't have to deal with).
What I'm suggesting is that if she (or another family member) could find a case manager who would do all the sorts of things that an adult child does in these situations, it might make the current situation tenable if not perfect.
I fully understand the panic engendered by having elderly parents 3000 miles away, and in the OP's case my understanding is that her visa status is such that she will not be able to return to the UK if there are problems (which I didn't have to deal with).
What I'm suggesting is that if she (or another family member) could find a case manager who would do all the sorts of things that an adult child does in these situations, it might make the current situation tenable if not perfect.