Struggling with 96 YO mother after 10 years...

It's impossible to keep ten years concise but will try. It's about that long since mom had a mild stroke. A very independent 86 at the time, a widow (my father) since 1997. No other men, regular church attending healthy attractive woman.
I'm only child (son), married, now 73 with my share of health issues from heart, kidney, spine, shoulders and hip and other surgeries. I have chronic pain history.
I maintain both of our houses, my wife and I take her where she needs to go and keep her shelves and frog stocked. She's a very particular eater as well as everything else. She's demanding, takes us for granted and still drives to local stores, PT and hairdresser.
Last year (Feb) she was scammed out $6000. She has always been gullible for the Publisher's Clearing House. I found out when she told me she was rich and had about $5million coming to her after sending money to some people she met on the telephone. I immediately contacted the police and she flipped out on me. Over the next month or so with the help of the bank we prevented another $40,000 plus from being transferred to the crooks. She refused to file a complaint, blamed me for keeping her from winning the sweepstakes. I am her POA and have access to her bank and other financials. I got the POA when she was recovering from an almost fatal UTI.
My wife and I discovered what a mess her finances were. This is just a tiny bit of what the last few years with minimal details. Anyway, she spends a lot of time and money on the internet. Yeah, that's right, the internet. So about a month ago the 5 YO computer died. She now wants me to buy her a new one. She's not only becoming forgetful but is accusing my wife and me of stealing from her account. She's been changing credit cards and accusing people of defrauding her and lying about charges she's made but says she didn't. Again, this is a drop in the bucket. So a little while ago she calls and asks where her new computer is. I kept cool and explained she had doctor's appt this week and she needed bloodwork. I raised my voice saying I had to go. The doctor's appt is a follow up from a previous complaint about itching on her neck and head which I just found out she wasn't taking the meds and was lying about it. You see, she buys thousands of dollars of vitamins from advertisements on the internet, forgets why or where she has them and thinks she has eye problems and brain damage that is causing the itching. Again, her doctor examined and prescribed meds she won't take and demands I take her back to the doctor. I'm cooked. I started seeing a therapist three years ago after she told me her will shared the estate with cousins of mine who she never sees. There's so much more...