You know how behind every great man is a woman? I'm going to be that woman.
~ Karen Waterford

Karen Waterford was the main villainess in The Good Mistress. She was played by Kendra Anderson.

Karen Waterford was the best friend and former babysitter of Sandy Cooper, as well as the wife of David Waterford, a political candidate who Sandy meets under the name, "Sam," and engages into a sexual relationship, but doesn't learn until afterwards that he is, in fact, Karen's husband. It is revealed that David had a previous fling with Ann Logan, who was found dead in a wooded area, and Sandy suspects that David killed her to keep her quiet. After Sandy goes to a secluded cabin to save Karen from David, she confesses to the affair to Karen, only for Karen to grab a knife and lunge after her, revealing herself as the actual killer.

Karen knew about David's affair with Ann, so she tracked them both down on several occasions. She invited Ann to take part in a photo session, only to chase her down the aforementioned wooded area, bludgeon her with a rock, and choke her to death. Karen later tracked Sandy down and killed her acquaintance to prevent him from talking. She also cut the brake lines to Sandy's car in an attempt to kill her. Regarding Karen's evil motive, she plans on living the good life after her husband gets elected, and she has been taking out anyone who gets in the way of that. Karen chased Sandy outside the cabin with the knife, only to be shot and killed by Sandy after David stops her.