narcissistic sister

I have a sister (one of 3) who is very narcissistic. I have only just realised this as I thought the word narcissistic meant something else, however, she fits the bill of all that I understand this word to mean. She will not admit to any wrongdoing at all and has fallen out with many of her friends. She blames everyone else for the breakdown of these relationships and her bad behaviour. Over the years she has verbally insulted many people including me to the point that sometimes I felt the relationship was abusive. Now she is systematically turning my other family members against me. If I confront her she says it is me being sensitive (which I am not). She also is very bitter towards anyone who has children (she didn't have any out of choice) and seems to resent anyone who is a mother or grandparent. We used to be good friends but now I can't trust her and although I still have a 'relationship' with her and speak maybe once a month. I'm at a loss what to do except maintain my boundaries.