Jan, I'm so sorry that you’re having to go through this.
I agree that your sister probably WILL attempt contact at some point, when she’s no longer getting any gratification from her current method.
My N mother often changes her approach, depending on what does or doesn’t affect me. This wasn’t the case as much when I was younger and in contact with her. Back then, she could see what was working, and would stick with what she knew was hurting me. Now that she hasn’t seen or heard from me in seven years, she has no way of knowing what affect her games are having on me, so she’ll try something new after a year or so of not getting the desired response.
I can also tell you from my own experience that the “your dead to me” routine is not out of the ordinary. My mother used to play “I’m not speaking to you” all the time when I was a kid, not just to me, but to anyone in the family she was angry with. I remember when I was a child, my father took a trip back home to South Africa so he could see his mother before she died. M was so angry that she refused to speak to him for an entire year afterwards. On another occasion, she accompanied my sister on a trip to New York, and they had an argument on the plane. After they landed, M made her “I’m not speaking to you” announcement, and proceeded to give S the cold shoulder for the duration of the trip. She acts just like a child having a tantrum when she does this, complete with foot stomping and pouting.
Long story short, I don’t think your sister is behaving outside of the norm for an N. I’m not an expert, but from my own experience with an N mother, I’ve found that the primary goal of an N is to elicit a reaction. If one tactic doesn’t achieve the desired response, then another tactic will follow.
Kathy