Doydie, your Mom is so fortunate to have so many people around her that love and care about her.
The hospice that my Dad was in allowed family to stay however long they wanted....even overnight.....but they did all the "caring" work such as changing sheets, giving meds and making sure he was comfortable. Will you and your sister have to provide all of your Mom's care or will the hospice nurses help, too?
You're all in my prayers. It's so difficult to watch a parent's health decline but I'm glad you have the opportunity to be there with her right now.