How do I resolve the conflict around my parents house with my sister?

My mother left her house to me because I took care of her and my father for years and lived with them. I have a sister, who lives in another state and who did not help us. Originally, my mother had left some money to me and intended to leave the house to me and my sister, but we spent the money on her nursing home care because she developed a terrible bedsore while in the hospital and needed skilled nursing care. She never came home because the bedsore did not heal, and the medical staff decided to stop treatment against her wishes, but she changed her will and left the house and its contents to me. My sister received 1/2 of the life insurance and some I bonds, but she told me that "if I don't receive one third or half of the house, I don't have a sister." Now she wants $100,000 from me, payable over 10 years as her share, and then she says she won't ask for anything else. I paid her over $300 so far this year, but some trees fell on the house, and I am trying to get the damage fixed before paying her any more money. Should I pay her the $100,000? She also wants me to sell the house when I retire and help her buy another house, help her husband start a second career when he retires, and she wants me to leave her the house in my will I had discussed paying money to sy sister with my mother, and she thought it was a good ides, but $10,000 a year is a lot for me to pay. My parents gave my sister a lot of money and material things, but it never seems to be enough. I don't know what to do. Thank you!