Stopping all contact with sister

[answers]

Mum died in 2010 - no other older relatives as parents divorced and grandparents also dead.... Sister always been quite domineering - even with own sons....
So about a month before Christmas she started saying things about brothers and mum on social media site. I expressed a wish that she wouldn't discuss like this as it was upsetting to read....
Suprise suprise received a torrent of abuse ... I remained calm but explained that I need a break from all the drama so no longer wanted to be in contact...
Thing is I don't feel at all bad about this .. it has been over a month and life is certainly more pleasant for me and my family ...
AIBU .. after all she is my sister ???

Answers . Your emotions are instinctive I believe, and since you said your self you "do not feel at all bad." That is a good sign you are doing what is right ... For you.
Things may change, IME it's good to keep a comfortable distance sometimes .

By an accident of birth you and your sister share the same parents.

That is not a good enough reason to put up with someone in your life if they don't add to it but instead cause problems.