How do I cope with my mother's poor behaviors, which have caused my home life to be depressing?

I first of all want to sincerely thank those of you who have taken the time to respond to my questions. I appreciate each of you. This site is so helpful and I appreciate being a member. My mother, age 86, has been living with my roommate and I for almost a year. She had open heart surgery and was ventilator dependent from her surgery during 2009 until her discharge from a chronic care facility last October. She had lived in Pennsylvania on her own prior to the surgery and I had my life in the DC area. The discharge planning was very traumatic for me. I even suffered two anxiety attacks which scared me to death. I am 61 and I think so far pretty healthy. Anyway, I was all alone with no family help trying to figure out the next step for my mother. A nursing home was out of the question. My mother continues to get stronger, has a sound mind, and if she were in a nursing home this would not work for either of us. No one cares for your loved one like you. Nursing homes are understaffed and enough on that subject. So I considered having her mobile home relocated near me in Maryland. That did not work. This home is too old to relocate and there are no mobile home parks near our residence. I checked into Assisted Living and found these are far too expensive. I thought about renting an apartment near our home where I could visit my mother everyday and monitor her in-home care by those when I am not there. I still work full-time. Anyway, long story short, after all of those considerations, my roommate (partner) said the only choice is to have my mother live with us. I was so relieved as the only other option would be for me to retire and move with my mother back to her mobile home in Pennsylvania and that was not going to happen. My roommate gave up her home office space and we arranged a wonderfully large room for my mother on the lower level of our home. My roommate was such a help to me. She would check on my mother during the nights to allow me to have uninterrupted sleep. She has done all of our laundry. She has ordered a closet for my mom and put it together. She has steam cleaned the carpet in my mother's room. Here is my major problem. My mother is not like me. Instead of being grateful that she has been called a "miracle" patient and make the best of living in our home, she is mean spirited and has never liked anyone except her precious "family" in Pennsylvania and me. Recently, I was at work and my roommate reported that my mother threw a "temper tantrum" because my roommate and my mother's CNA were outside of my mother's room talking. My roommate was giving the CNA instructions about what do to if a repairman came to our home. My mother threw her walker and got mad. (My mother denies this behavior.) I have personal knowledge that my mother does not like it when my roommate comes into her room during the days and talks with the CNAs. My roomate if very vivacious and has a funny personality. She has two little yorkies and you would think that this would be a pleasant environment for my mothers. Oh no. She is a loner and always yells "shut the door" whenever my roommate enters her room. So I came home from work after a long day last week to hear my roommate explain that the CNA that day had tears in her eyes over my mother's behavior so my roommate tried to explain to my mother such behavior is unacceptable. My mother in turn denies throwing her walker and so what does this do? It puts me in the middle. I told my mother last Saturday that I feel like running away from everyone and that it is disrespectful to me for her to live in our home and cause this dissention. I told her she has never gotten along wth anyone but now she is in our home and if my home can't be my soft place to fall, what am I to do? My mother would not admit to her behavior and all she could say is that my roommate "laid into her." So now I am upset by all of this. My roommate has chosen to stay away from my mother and I have told my mother clearly not to expect my roommate to come into her room because she is taking care of her emotions and I support this. After 3 1/2 years of living and breathing hospitals in support of my mother and all that I have been through emotionally, I don't feel that by any means I deserve my mother not to understand what this is doing to me. If I try to talk to her, she says she is"nervous" and won't communicate. The one thing that was going right in this situation was the help I was getting from my roommate. I don't blame her for not going into my mother's room. It is apparent to both my roommate and I that my mother does not like my roommate. I told my mother if she thinks I am going to retire and live out my days one on one with her she is mistaken. Sorry for the long message. I am angry at my mother and today I took off work this morning to take her to yet another doctor's appointment. I feel disrespected.