I will definitely pray for your sister and whole family. My family went through the same thing with one of my sisters this Easter will be 4 years ago. May God give you and your family the strength to make it through this very trying time. I've also lost my mom since then and some days think I just can't go on. I watch this video every morning to start my day and it certainly has helped me.
YouTube - "I Cant Even Walk (Without You Holding My Hand)" By Gordon Mote