Sadie Kavanaugh was the ex-wife of Internal Affairs detective Jon Kavanaugh. She has a history of mental illness. In the episode titled "Kavanaugh", she makes up a story about being raped to get the attention of her ex-husband. She even falsely accused a man who she had seen on a flyer earlier in the day, but when her story crumbled, even her ex-husband had to call her on her erroneous story.
Later in Season Five, she sleeps with Vic Mackey in an attempt to get Kavanaugh's attention. Her plan worked, and eventually Kavanaugh tries to get back at VIc by seducing Corrine Mackey.