Dear amk-
This is going to be a very difficult time for you and your family. What I suggest is that, hard as it can be, start getting some family pictures of happier times together and take them with you to the hospital. Spend some time with your sister going over your life together and share some good memories with her. Let her know how special those memories are for you. I for one never give up hope and do believe in miracles and I also know the value of humor and lighter moments. While she is awake, share these lighter moments and memories with her. Get her smiling again! It will be healing for you all. Love and prayers - Kris