Estella Havisham is a one-off character from the episode "Pip". Like Pip, she is a literary counterpart from Charles Dickens' classic tale, Great Expectations. Estella is the daughter of Miss Havisham, and was raised to break mens hearts.
Background
Estella first meets Pip after he answers a job offer in the newspaper. Pip is hired by Miss Havisham to be a playmate with Estella. She is very surprised to find that her game of "whack the blond boy over the head with a log" is one that Pip and his sister play often. Estella treats Pip cruelly, calling him many nasty names. Though she is cruel, Pip falls in love with her. After being sent away to become a gentleman, Pip reunites with Estella. He tells Estella that he believes that he is in love with her, but is heartbroken to find that she has a seventeen year old boyfriend who owns a car. Pip soon discovers that Estella was raised to break hearts so that the tears from all of her ex-boyfriends could be used to fuel a machine which would combine Miss Havisham's soul with Estella's body. Pip tries to convince Estella that she is not cold hearted by giving her a baby bunny. Estella breaks the bunny's neck, and Pip offers another (which she also kills). Estella continues to kill the bunnies offered to her by Pip, but stops after the twenty fifth. Pip claims that she has a heart due to her inability to kill twenty six baby bunnies and unhooks her from Miss Havisham's machine. Miss Havisham dies in a fire resulting from the machine malfunctioning, and Estella accepts her love for her "small testicled darling", Pip.
It is not stated to whether Pip and Estella's relationship continued after the episode, though is highly likely that the events of the episode are not canon to the series.