At my age... I have issues with my mother?

I am 61, my mother is 90. I look back on my life and how I used to worry about her dying. She always seemed to be unwell when I was a child and I spent so much time worrying about her. I look at her now and I think why did I waste so of my childhood worrying about her? She is still here at 90 and what an acid drop she is. She has turned into a horrid woman with a very negative, suspicious attitude. I realise now she is and has suffered with depression for a lot of her life. My sister has a mental illness after suffering a nervous breakdown 24 yrs ago. My mother now lives with my sister and it is a very negative household. I have tried to get services in to help them, but the reject me and my help. My mother was always wary of my sister and yet she chose to live with her after giving up her own home and live with my sister. My mother is verbally abusive towards me and then if she happens to be 'caught out' she changes her tune and denies having said nasty things. She is waiting to go into aged care. Her home still has to be emptied and cleaned. It is up to me to organise this. I just want to be free of her, the truth be known, she is constantly on my mind and when I have to see her and my sister, I get a knot in my stomach. Would I be awful if after she goes into aged care if I don't visit? She has turned me against her and I don't trust her. I am the odd one out in my family.... mum and my sister smoke. I am a non smoker. My interests are different, I still go out to work, I have a husband. My sister is divorced. She was in hospital recently with her mental problems and I read a journal of hers I found. It was sickening to read and any respect I had for her has completely gone. She wrote it when her married was breaking up and it was all about her problems at the time, obsession with money and her almost ex husband and her jumping into bed all the time. I wish I hadn't read it, but I did and every time I look at her it makes me sick. I don't like my sister or my mother very much. They are a miserable negative pair and I wouldn't care if I never saw either of them again. I have nothing to talk to them about. My mother is happy to sit and smoke and do puzzles all day or talk at me when I do see her. My sister is suspicious and asks stupid questions. I realise they are both very sick, but there is nothing I can do, or can I?