Answer the following question: Found the following article online, use it to answer the question: Who is the sister of the spirit that the psychic bookstore clerk helps?  Elizabeth Masterson, a young emergency medicine physician whose work is her whole life, is in a serious car accident while on her way to a blind date. Three months later, David Abbott, a landscape architect recovering from the sudden death of his wife, moves into the apartment that had been Elizabeth's, after 'discovering' it in what seems to be a fateful happenstance. Elizabeth's spirit begins to appear to David in the apartment with ghostly properties and abilities that make it clear that something is not right. She can suddenly appear and disappear, walk or move through walls and objects, and once takes over his actions. When they meet, they are both surprised, as Elizabeth is still unaware of her recent history and refuses to think she is dead. David tries to have her spirit exorcised from the apartment, but to no avail. Since only David can see and hear her, others think that he is hallucinating and talking to himself. David and Elizabeth begin to bond, as much as that is possible, and he takes her out of town to a beautiful landscaped garden he designed. Elizabeth tells him she senses she has been there before, and in fact, the garden was something she was dreaming of in the opening scenes of the film, where she was awakened by a colleague from cat-napping after working a 23-hour shift in the hospital. Together, assisted by a psychic bookstore clerk, Darryl, Elizabeth and David find out who she is, what happened to her, and why they are connected. She is not dead, but in a coma, her body being kept on life support at the hospital where she used to work. When David discovers that in accordance with her living will, she will soon be allowed to die, he tries to prevent this by telling Elizabeth's sister, Abby, that he can see her and what the situation involves. One of Elizabeth's young nieces is revealed to be able to sense her presence as well.
Answer:
Abby