How do I deal with a mother who is constantly negative and rejects any treatment/medication?

My mother is 79 years old going on 109. My mother has a number of medical issues but refuses to address them with any treatment (she has great insurance!) and even after the doctor and I suggested she get on an anti-depressant/anxiety she accused us of wanting to turn her into a drug addict. I moved into her home to help her as she refuses to move anywhere else; while I lived out of state, she would call me first thing in the morning or within minutes after I left work. If I did not answer the phone, she would start calling my children and everyone else in the family to find me (this after calling me every two/three minutes for about an hour). Once, I got on the phone she would say "I cannot go about my day or be happy until I spoke to you".

I have tried setting boundaries and she will punish me to no end - shaming, guilt, denying herself food, whatever will get a reaction...even my brothers do not want to come visit or barely call her. Just two days ago, in the kitchen while I was having a conversation with Dad she screamed "do not talk, you are distracting me".. since Dad was not wearing his hearing aids she shouted again and all I could see was rage. Went out with a friend today for coffee and a walk with the dogs and I returned to "you knew I wanted to go out and you went out without me wasting gasoline and coming back at this hour -7:30PM- fine, I will go out tomorrow and I will do what I have to do on my own and I don't need you". Another example, she forbade me from taking my dog to the beach because every time I take her out she comes back with hurting joints and it is obvious I do not know how to care for her - for the record, my dog is 17 and still loves to go out-.

My mother undercuts me at every chance she gets, shames me even for the way I dress, the things I buy, the things I like to eat and brings out the sacrifices she has made for me ("not to rub it in your face but") and how that has affected her life. Even though I have traveled around the world and even lived overseas on my own my mother still treats me like I am incompetent ("no, that is not the way you wash lettuce because.." "you would not be in this position if you had", "if you had only listened to me"... you name it) - inefficient, incapable, dumb and often reminds me she is a fashionista (even though there are days she will not get out of her pj's) and at my age I still do not know how to dress appropriately and the way she wants to see me.

While my mom was on Prozac (a relatively recent prescription) she was so nice and mellow, a joy to be around then I went to visit my children and she stopped because "I do not need those things, that is for people who are weak of character and I am not an addict" (sigh!) took her to physical therapy a few times and she was doing great and feeling much better then she stopped "they only want to make money of me, I am not going to go" - when it was suggested that we try physical therapy at her hospital she said "it is too tiring to go, I am fine with my Tylenol" even though her doctor recommended that she take Robaxin/Metacarbemol for her pain.

Everything I try to do to enhance her quality of life, my mom, shuts it down because "I know better" - I am seriously considering going back to my family, her attitude is so negative and nasty towards me (not my brothers though) - while her grandchildren were off limits for this negativity and nastiness, my Mom has begun to spill this "life poison" into them....

Please help me, any advice, suggestions, anything, I am desperate. As I am in my room writing this, my Mom came into the room to remind me what a disappointment I am to her because I took the afternoon to spend it with a friend and my dog.

Broken (but still resilient!)