The Sleeper is a 2000 British film featuring a malevolent woman.
Based on the 1998 novel by Gillian White, the film tells the story of Violet Moon (Eileen Atkins), a spiritualist who is trying to persuade her son (Ciaran Hinds) to keep the family farm despite the financial difficulties he is experiencing.
As Violet and her family are gathering at the farm for Christmas, a woman Violet hasn't seen in 60+ years turns up.
Violet has never told her family about the stepsister she once had, that is, before Violet pushed her new stepmother off a balcony and blamed the older girl.
One girl was institutionalised as a child. We don't know what happened to Violet after her father killed himself.