Do I have any legal authority while living at my father's house?

I currently reside at my father's house in Media, PA. I have lived with him here since April 2010. On May 6, 2014, my Dad fell and has a serious brain injury as a result. He has been hospitalized in ICU since that day however he is due to come home on hospice in a few days. My Dad is currently 88 years old and his health is rapidly failing due to complications from the injury. Until the date of his injury he led a completely active lifestyle, surprisingly spry for someone his age. There are 5 children in our family and all of us get along very well except one (my younger sister). Unfortunately, over the years she has been terrible to our family: stealing things from my father's house, taking money over and over again from our father, causing many problems in general with each and every other family member. During our Dad's recent hospital stay she has been especially nasty and caused as much trouble as possible regardless of his condition. Since our Dad likely has little time left, we wish only to make him as comfortable as possible when he arrives home. Since I live here at my Dad's house do I have any legal authority at all to keep her from coming on the premises? One of my older brothers has power of attorney for my Dad's bank accounts which is a relief however he has told me that he does not have any power of attorney over the house and property. Our Dad does not have a living will and no one has power of attorney for his medical condition or issues. (That's caused many problems which my younger sister has taken advantage of many times). Please help?!! Thank you.