Is it wrong of me ask for a respite break?

A fellow caregiver asked...

My mother had me at 14 and she made my youth less than desirable. I was told that "if abortions would have been legal, I would not be here". Foster homes, string of step fathers abuse etc...We have never had a good relationship. If we were not related I would not be her friend. Fast forward 40 years...My mother has end stage COPD and cardio megle. My first husband died 8 years ago and my son was murdered 4 years ago, I remarried and thought that I was putting the pieces of my life back together. We lived alone and had a wonderful relationship. My mother's neighbor found her on the floor and we took her to the hospital, she was in respiratory distress. We were told that she cannot live alone....what to do? The only moral thing is to take care of her. She did not like my home for many reasons, we could not live in her apartment. We sold our home and purchased a home that neither my husband nor myself care for, because Mother thought it would be good for her. I have quit my job and wait on her hand and foot. This has been going on for 2 years. She complains about the food, the way I clean, the way I do the laundry, my husband, she has taken over the entire house. etc... I feel like I want to run away. I am not comfortable in my own home. I find myself becoming more and more withdrawn. I try to stay away from her as much as possible. Mother refuses to quit smoking and she is angry with the world. I have 2 brothers, they live too far to help and a sister who live 45 minutes away. My sister comes over once a month to get a check from Mother and leaves. My sister can do no wrong in my Mother's eyes. My Mother has chosen my sister as an example to my other siblings and myself. And yet, my sister does nothing for our Mother. I am tired, lonely and my marriage is suffering. I have lost a child and a husband. Do I not deserve a life and happiness too? I feel an enormous guilt and responsibility. Mother did not care for me as a child, let alone as an adult. Why do I feel it is necessary to care for her? My Mother left our state when her own Mother was 70, and when I said something to her about leaving Grandma, I was told, "I have a life to live don't I"? I wonder if my Mother thinks about that now? Thank you for letting me vent. Sometimes it just seems overwhelming...