@mrmj As someone who is on the list to move into a retirement community specifically because it provides a continuum of care, let me offer:

Who has agency here? In other words, whose decision is this, really? This is a tricky question if your mom is well into dementia. If her issues are entirely or mostly physical, however, it seems to me that it's her choice to make. If she makes an unsafe choice, still hers. If she regrets it later, still hers. If you itch to say "I told you so" later, still hers.

I was the lead remote caregiver for both of my parents before they died, both of dementia, and the only decision I now regret was how long I delayed shifting entirely to palliative care. The rest of it was basically their choices, right or wrong. When my mother hit end-stage dementia, we still tried to make the choices she would have made, based on the person she was when she still had the ability to speak. Could my parents have lived longer if I and my sister and our two step-siblings had made different choices? Maybe. Would they have been happier? I doubt it.

When did we decide that we should treat the elderly as if they are toddlers?

A few practical observations:
-- We had frequent family conference calls, so we were all up to date, which also gave us an opportunity to discuss what was going on. My mother was not on those calls, which left us able to have difficult conversations.

-- None of us cared how much money was left in the end. We all agreed that the point was that it was theirs and for them to burn it. If that isn't true for you, you have another challenge.

-- It is fair to ask her how she plans to ensure she has the help she needs around the house. It is also fair not to let her decide that the solution is for one of you to move in or be over constantly. You have agency, too.

-- Someone needs to have legal authority to make financial and health decisions if and when her doctor decides she is no longer capable of doing so. Those two people need to hold themselves accountable for staying informed, and need to be given the rights and authority to do so. In my case, health decisions were less of a problem than financial decisions, because my mother prided herself on her financial acuity and was unwilling to let go of the reins. But we got through it after she started regularly bouncing checks, with the help of her financial advisor and some understanding bank staff. Whoever backstops each of these functions needs to keep in mind her agency, which is easier if she sees them as supportive and helpful rather than people who cannot be trusted. This can be a problem if the person she wants to delegate each of these responsibilities to is not the person who feels they should have been chosen. It might be helpful to encourage her to confide her choices to a friend, who can have the conversation with the kids. The right friend (or religious leader, or social worker) can be a good facilitator.

-- She will make mistakes and bad choices, because don't we all? If she continues to trust all of you, though, she will come to you for help. If she starts distrusting you (because, for example, you have taken away her control over her life), she won't. Is that better or worse than the consequences of taking control from her? Do you want to be mostly the police and warden, or mostly her children?

-- She may find that one of the mistakes she makes is to isolate herself. You have every right not to own that choice. If she wants to live in a bubble and tries to drag you into it, thereby cutting you off from your own life, don't let her. You don't own her bad choices any more than you own her good choices. That's what agency is about.

-- We all need to die from something, sometime. I would personally rather die (or break a hip) while still in charge of my life, even if it means I die earlier. So tired of quantity of life being valued over quality of life.

Finally: There is no good solution for quality of care, because we have run out of people who want to do this work for what we are willing to pay them. In the end, my father was cared for in an institution, and we paid someone to oversee my mother's care when we hit the stage of 24/7 assistance -- in fact, if she or one of you can afford it, there is an entire profession of people whose job it is to act as independent oversight of care. But both of them lived in the tri-state area and died a decade ago. There is no way on earth my husband and I can expect equivalent home care in upstate New York today. So all you can do is all you can do. (It helps, I'm sure, to be rich. But then, it mostly does.)