I have never figured out the compulsion for people to stay in their own homes when (1) they can no longer physically manage, (2) cannot afford the upkeep, and (3) it has become a safety hazard for them to stay. For many seniors, the quality of their lives will improve dramatically if they are in a safe, secure environment. I do know several seniors who told me that they did not know why they resisted for so long....they had such peace of mind once they moved to AL.
Do you have durable POA? If so, your mother's doctor must evaluate her for a determination if she is competent to conduct her own business in a business like manner, (which her retail therapy already shows she is not capable of), Once you have such a written statement on the doctor's letterhead, then it is time to take over your mom's bills ect. for her own financial protection. Her doctor also needs to tell her that now is the time for her to trust you. Does your mother feel depressed after she does all of that spending and realizes how much money she spent? Has she ever used retail therapy like this before in her life?
Do you have medical POA. I sure hope so because, the above will be much easier to get going and the doctor will be at liberty to talk with her about her health with it.
If not, then both the good and bad news is that your mother must have protection from herself and if she has not set up legal means for someone like yourself to step in, then someone must file for guardianship with is very painful, humiliating, etc.
It does make me very angry that parents force the hand of their adult children in this regard....I think they are being very selfish. If they did more advance planning and gradual downsizing of their lives, it would be an easy transition for everyone, and they would have some "choice" in their living arrangements, instead being forced out when they become totally incompetent to handle their own affairs.
As for me, I already have a headstone laid for my husband and I back in the state where we were born, next to my parents' graves so that nobody is burdened by having to take care of this for us. I took care of this matter when I was about 45. Wish more people would do the same to reduce the burden on their relatives.
You may have to find a way to stop the shopping or she will be out of money for any home health or facility care, plus have a huge cluttered mess as it progresses into hoarding if it hasn't already. You could start returning clothes she forgets she has bought, maybe? Legally speaking, it sounds like you need a power of attorney or even guardianship.
But, I did not answer your real question, Why? Because instinctively people know that giving up driving and giving up their home are great big steps closer to losing everything they have. It may be inevitable, but who wants to admit it? And who wants to go to a doctor to have it confirmed?
There are also agencies that come into the home and maybe even get people to day centers, if she can have that much autonomy it might be good.
I am an only child had to make the decision that the medical people were right and my mom could no longer be expected to return home after two years in various facilities trying to rehab, and then actually empty out and sell the house for her. It was awful. I hope you have more help and I hope there is a way for you and your mom to be happy. My mom is soemtimes happy and enjoys our visits, etc., but she still just kind of tactily assumes, even after three years of being unable to care for herself or mobilize, she will still return home to live independently someday. She is not reallyaware of how long it has been - she has pretty bad vascular dementia and diabetes too. I wish it was easier.