What can I do if my mother's house is no longer safe for her?

I live in my mothers 3 story house (3rd floor apartment) and pay her full rent. My mother is 79 yo and high functioning as far as physical ability. She does take meds for High Bood Pressure. My mother has always been a difficult person and now it is amplified. You say white, she says black. I work full time (sometimes 12 hour days), I take care of all the heavy lifting (laundry, grocery shopping, errands, house maintenance, washing floors, cleaning her house). I can't take care of everything due to finances. Her finances are better than mine. My mother complains about her health - a headache is a brain tumor, a sore muscle is a broken bone, anxiety is a heart attack - I've taken her at her demand to the hospital 12 times over the last 4 years. The drs run everything necessary in an emergency room and can't find anything wrong. She gives her dr a hard time, every visit is my mother trying to tell her dr she doesn't have to take her pills. My sisters (I'm the middle daughter) would get a call from her and yell at me to take her to the hosptial each time. The last visit to the hospital I forced my older sister to take her, cause each time it's a false alarm. My sister sat in the emergency room for 14 hours while drs tried to find something wrong with my mother. They can't. Since then, my mother doesn't demand to go to the hospital anymore. However, it appears she has turned her focus on her old dog, demanding I take her and him to the vet at least once a month. He is 17 and has health issues, each time we take him, the vet says...he's old that's all. She will make up things to make me take him but tells a different story when we are at the vet. She did the same thing with taking her to the hospital; says she can't breathe, won't let me call 911, I'd drive to the emergency room, and she'd tell the triage nurse something else (i.e. I hurt my finger) etc. Just telling you this as background. If I confront her about it, she screams and holds her chest (she has no heart problems) and storms away. She says (I know that sounds resentful) she can't manage the stairs anymore and I've seen her shuffle her feet on the last step and then turn to me as if to say "see?" Yet, what I just witnessed wasn't a slip or fall, just a deliberate shuffling of her feet. Then she will call my sisters and say she fell down the steps. However, I am realistic...she can't go up and down the stairs easily. The house is getting run down because I don't have enough time or finances to maintain it. I have to wash the floors and clean late at night, because she will walk on the floor while I'm trying to wash it, etc. I do the laundry, grocery shopping and maintenance on the house. I have to argue with her if a plumber is needed or the cesspool needs pumping, or fix things myself if she won't call someone. I depend on her to pay for these things in her house, unless I do things myself. Because I just don't have the money to pay for maintenance on a house. Now that my older sister has witnessed a trip to the hospital for no reason, she is more open to the issues i'm facing and is trying to help. My 2 sisters and I are trying to convince her to sell the house as neither she nor I can take care of it anymore. She won't budge and yells and uses guilt about her rough her life has been and ours shouldn't be easy. She has gone so far as to suggest, I quit my job and end my relationship with my boyfriend (of 15 years) to just care for her. We have told her we don't want the house, it's too old and expensive to take care of and our life styles aren't conducive of owning a home. None of us are married or have children (which is another story - marriage and children is horrible according to my mother, we've been told that all our lives). We have suggested, that me and my younger sister and she get apartments in the same complex. She doesn't need full time care, although she says she does in one breath and then won't let anyone else come into the home to clean or do anything for her. We explained that her bank account, sale of the home and social security would more than pay for rent and needs, and we would help with anything else. She refuses. We have offered to rearrange the house (her 2 floors) to make it easier and do a full cleaning. She refuses. She will also only let me clean what she wants me to clean and the house is getting more full of clutter. Now she is sleeping on the couch on the bottom floor which can't be good for someone her age. Now I can't even wash the kitchen floor, cause she hears me come down (no matter what time) and will walk on it while I wash it and it's wet and scream and cry if I tell her not to until it's dry. Just an example. I'm tired, stressed, my boss is complaining about all the time I'm away from work. When I try to explain it to her, she screams, cries and that she's mother and she comes first. Help...what can we do to convince things have to change?