Problems with a sister who cooks for elderly father

I need help understanding my large family. First, they all dislike me and talk about me to each other all the time. When I think I have had a good and mature conversation I later hear how upsetting I was. One of the most troubling moments for me right now is that an older sister does not allow anyone to see my father's bills or personal information. Every time I bring it up, she complains to all my siblings (we are a large elderly family). I am the youngest sibling that I am to blame as she does not convince my 99 yo father, "For no one to touch his bills or bank statements/deposits/withdrawals, etc." She also will not show anyone my father's Will and Testament. I have asked for over three years and she pretends ignorance and innocence. Help! She complains that my father wastes all his money as there is nothing left for us to pay a caretaker. My other siblings are older and do not understand how to deal with the problem. They all tell me to leave my sister alone.