Why the h*ll am I bothered by this. I KNOW this is how she is. I guess somewhere inside of her I expect to find a real person with a heart.
You're feeling justified anger that is magnified by old anger at old issues caused by the same person. It's like picking at a wound that hasn't healed fully. Unlike some, I do not believe there is good in all people. Your mother chose long ago to flush any and all goodness from her heart and what is left now is only a shell that is unrelenting and cruel.
My mother was the same. At some point you must choose whether to accomodate such a person in your life or whether it is better to prune them out like a dead tree limb. Either choice is painful, but you must decide for yourself.
When I was forbidden to attend my mother's funeral (on threats of violence to Nina and me), I waited. I put my mother up on a shelf and left those feelings and the need for closure alone for a while. Not until 4 years later did I finally go to her gravesite. I took my newborn daughter. I 'showed' my daughter to my dead mother; I told her about my name change and how my family would now be separate forever from hers; I told her all the things I was angry about , all the horrors she had visited on me in my life and cried all the tears I had held back all my life. Finally I left her grave by telling her my children will never know what I know. It was one of the most cathartic and healing things I ever did.
My point in relating this Lee is to show you that some things are beyond our control. But not everything. Decide best how you want to memorialize, and grieve, your sister's death. There does not have to be a time limit (I was content to wait 4 years). Your mother cannot control you any longer, nor can she control your grief and how you choose to express it.
Let her insanity go. Release it from your life. Verbalize what you are angry about, write it down here, or in a journal that will help begin the process of purging. You have every right in the world to be furious with her, for all the atrocities she has brought into your life. THAT is why you are 'bothered' and sadly she will never change. She will always push your buttons. I chose to cut the insanity of my family out of my life and I've never regretted it.
Sorry for rambling, but I hate to see you hurting.
Chris