A question about my rights to visit my father who has Alzheimer's. I'm his daughter from his first marriage. His 4th wife won't let me visit him.

My father has Alzheimer's disease. I am his daughter from his first wife. My Dad is now on his fourth wife. He doesn't have children from any of his other marriages, including this current one. My father's fourth wife is denying me the right to visit my father. She has evened threatened to get a restraining order. I want to know what I have to do to be able to see my Dad. I love him, I miss him. He and his wife live in Buffalo, New York. I live in Burlington, Vermont.