I hope it all works out for you ForeverLonelyGirl. I know how you feel. I had a complete shut down last Christmas, horrible because no one understands and most people dont know of my MI. Ive done okay this year much to my amazement.
One day your sister may have a change of heart.
Have a wonderful Christmas and take care of yourself, dont stress too much.
Remember, Grandmothers are very special no matter what.