Cathy Durant was a good character on the show, I think. She starts out as a U.S. Senator from Louisiana but she plots with Frank Underwood to become the new Secretary of State.
And the plan works, and she does well in her role from what the story portrayed for the most part. She works for both President Walker and President Underwood. She tries to pretend that she’ll be Frank’s running mate in the new election.
But she plots like Frank would, to take the nomination from under his feet. It didn’t work out too well for her here.
And her relationship with Frank sours to the point where they basically hate each other. Her big mistake was letting him know that she was going to testify against him and it was not going to be good.
So he pushes her down the stairs where the cameras could not see. I thought she was dead, but that wasn’t the case. He just knocked her out good.
It seems she lost her memory but she lets President Claire Underwood know that certain memories were still there.
And at the end of the series, she is shot in Europe on Claire’s orders. I rather hated that.