Gaslit woman kills her husband

A woman is set up by her husband to appear crazy. (I think he hired people to be his friends and family at their wedding.) He had her committed to a mental hospital. At some point he tells her that all cells in the body are replaced every seven years so he wasn’t really the same man she married anymore. At the end of the movie she kills him when he visits her at the mental hospital. She had already been declared insane so she was going to wait a few months in the mental hospital and then be “cured”.