My mother is 78 with a sufficient monthly income and a very healthy portfolio, but has become panic-stricken and obsessive about the notion she is in a "financial hole." My husband and I relocated from our very good jobs in Chicago to be near her in Kentucky, as she was needing more help, but no matter what we do or say she is like a broken record about her finances. I try to reassure her, and we even went to her investor to reassure her, but she's absolutely beyond reason. I am at my wits end with her. Her negativity and irrational panic makes me very resentful, as we gave up quite a bit financially to be close and help her, and she seems not to recognize that. I have no idea what to do with her, but she's about to drive me back north!
I imagine your mother would be hugely insulted if you were even to hint that she is losing her mind? So instead, perhaps ask her to attend a clinic for a wellness check to rule out any problems that might interfere with her independence later on. Stress that this is to help her keep well, rather than suggest any problem that she might indignantly deny.
Thinking back to when she pleaded with you, really, to move closer to her, what seemed to be uppermost in her thoughts then? It does honestly sound as though her peace of mind might have been heading into the tank for quite some time.
I sincerely hope that if I ever lose executive function or, as my sister says, go ga-ga, that family will recognize it as not the real me, and try to get me help.
I know what you mean about being resentful. My parents decided to keep living in their home yet didn't want to pay anyone to help them... they looked toward me and here I was a senior citizen myself, I had my own age decline issues. Many times I wanted to go running into the night screaming.... my parents could have easily paid people to help them.
I remember one time my Dad said I will get the inheritance... and I remember saying "if I live to see it.... you and Mom probably would out live me".