Wicked (1997)

Casa Del Norte is a snobbish, upscale community where Ellie lives with her parents, younger sister and Swedish au pair. They all hate it except Dad, who is having an affair with the au pair. So Mom has an affair with the next door neighbor, until she is found bludgeoned to death on the kitchen floor. In a Hitchcockian twist, Ellie's grief gives way to a twisted obsession to become her mother as well as the object of her father's desire.