Hi Brooke:
I know it hurts.
When I first left the JWs, my parents threatened me with shunning. They even lived up to it for a little while. However, over time they have lightened up on this significantly and they even call me from time to time. And, last year they even came and visited me.
In any case, it could be that your sister and mother just had a knee jerk reaction due to the JW programming but over time her connection to you via blood and family ties will win out. I know that it does for many JWs. It just goes to show you how unnatural the shunning thing is for many people particularly over issues like buying Christmas gifts for your kids....
I think you handled the situation very well and over time your sister and mother may recognize how silly they acted with all of this.
You, your sister, and your mother are in my prayers,
Jeff Schwehm
From Sheboygan, WI
www.catholicxjw.com