MIL (90) lives alone and is 200 miles away, has dementia and is verbally abusive and accusatory. What do I do?

Accusatory to myself, my husband, granddaughter, all. She keeps all curtains drawn in her house, so that no one can peek in at her and so the sunshine does not fade her furniture. It is like a cave inside, cold and dark in the winter, warm and muggy and dark in the summer. She keeps the heat at 64 and refuses to use her air conditioner until temps break 90. Her freezer is packed with food that she no longer prepares for herself. I arranged Meals on Wheels to come for her M - F (which has turned out to be a Godsend). I order groceries online for her to eat on the weekends. My MIL has no friends. She has called the police on all of her neighbors for imagined wrongdoings, to the point that the neighbors have ceased communications with her. The police at one point were calling us as often as weekly to update us on her accusations, all of which were unfounded. She has accused the neighbors of poisoning her trees, of flying helicopters overhead and dropping pine needles from the copter... the lawncare people of sneaking onto her yard in the middle of the night to spread grass clippings about... the grocery store delivery service was accused of stealing a spatula, toothpaste and a mirror from her wall. We had to find an alternative food store to order groceries from for her. Now she is accusing either that food store or one of us of sneaking into her home in the middle of the night to steal her yogurt. The police calls seem to have quieted down lately. Now she is accusing myself and my husband of stealing candle stick holders from her. She accused my stepdaughter of stealing $1500 in cash which she stated was in a bag in her closet, along with her "pretty silverware", which she states my stepdaughter replaced with "ugly" silverware. She also has accused one or all of us of having stolen corn cob holders, a mixing bowl, mixing spoon, pictures off the wall... and on and on and on. We have seemingly good conversations over the phone, my husband calls once a week, I call once or twice a week. We no longer encourage our daughter to stay in touch, she is now 24, but was the brunt of accusations when she was 19 and we feel it is unhealthy for her to be exposed to the abusive accusations. Last summer her condition reached a low point, she was not eating, had elevated blood pressure and was more disoriented than usual. We arranged for her to see a doctor, (she had not seen one for 5 years, after her GP died) She strenuously objected to seeing a doc, however we were able to convince her that by seeing one, she would increase the likelihood of her being able to remain independent in her home as she strongly desires to do until she passes away. She was diagnosed with mild to moderate dementia, although she aced her cognitive examination. The doctor was able to discern through talking with her that she was very depressed and that many of her responses appeared practiced and, well, artificial. So, she was prescribed Remeron, Aricept and Lisinopril for the blood pressure. The doctor also decided she was best suited for home visits from him as well as a psychiatric nurse to visit once a week. MIL refused any additional intervention (aide, companion - refused ). She has been a Model patient for the doctor, answering questions appropriately, etc. She has occasional issues with the psych nurse, who calls whenever there is trouble. The problem is usually non-compliance with meds. MIL believes that since she didn't need meds 10 years ago, that she doesn't need them now. To date, I have been able to make MIL understand how important it is to take her pills and to see the nurse. Oh...there is so much to say.... so many issues....I could go on forever... She is currently calling me a crook to my husband, calling my husband a crook to her 93 year old ex-husband (who no longer will speak on the phone to her, because of her abusive ways - she leaves vicious messages about my husband, my step-daughter and me for him to endure listening through... he will not block her calls in the event she needs medical assistance or something should she reach out to him for that, he elects to remain somewhat available so that he can alert us should the need arise). At the time I am writing this she will not speak to me or my husband on the phone...I would not be so concerned were she living closer to us or if her mental health was not declining so. I really do not know what to do to help her and I worry about her social isolation and increasing paranoia. The doctors concede she has dementia but have stated she is still competent to make decisions for herself, which in itself is questionable as we have had to unravel multiple incidents involving irresponsible spending and investing with disreputable people (one of whom is now in jail for ponzi scheming millions from people just like and including my MIL). I think I mostly needed to vent my frustrations and get this stuff onto paper, however any suggestions or ideas to make life easier for everyone involved is most appreciated. Thank you for listening.