Were you ever close? if not, just be civil. If yes, I can share what i do with my mother. She became more depressed and anxious helping take care of dad (he had lots of hired help) and I became her scapegoat. In some blowouts she said HORRIBLE things to me and was just awful, but again would not get help.
I detached. I am polite and kind, but have invisible armor around me. I keep calls and visits shorter and less frequent. I don't share anything too personal. We were close once, but the relationship eroded over a number of years and a number of instances where she could never own anything she did and said.