But in the process, she will have to shed her "sweet girl" persona and embrace her darker side to fully embrace the role and to please her demanding and sexually aggressive director.
Her metamorphosis is so complete, that Nina eventually develops webbed feet, bird-like legs and sprouts feathers and wings to actually become the black swan.
"It was intense and disturbing and fascinating and mysterious, " said Nadine Kaslow, vice-chair of the department of psychiatry at Emory University and psychologist to the Atlanta Ballet. "What was a hallucination and what was real? When people are psychotic, it's difficult, even as a therapist, to know what's real and what's not."
Nina, who constantly strives for perfection, lives with her controlling mother Erica, played by Barbara Hershey, who gave up dance to have her daughter. They live in a tiny New York City apartment, cluttered with her mother's narcissistic paintings.
When the ballet's artistic director decides to replace the aging prima ballerina for the new season production of "Swan Lake, " Nina is his first choice. But she has competition in new sexually open dancer Lily, played by Mila Kunis.
After securing the role, Nina is asked to "lose herself" to play the black swan, and so she does.
In visual hallucinations, she sees a black-clad version of herself across the subway platform and again in the maze of hallways at Lincoln Center. Even the pink stuffed animals that adorn the bedroom she shares with her neurotic mother seem to come alive and mock her.
She conjures up an array of fantasies and delusions, including a lesbian love scene with Lily.
"As a movie fan, it held my attention, " said Dr. Steve Lamberti, professor of psychiatry at University of Rochester Medical Center. "It was poetic in a way, showing this transformation gone wrong."
But speaking as a psychiatrist, Lamberti said the film did not accurately depict schizophrenia, as has been widely speculated, but "does present a reasonable portrait of psychosis."
"People tend to be scared of things they don't understand, " he said. "If you have never treated or observed a person with psychosis, it's upsetting."
Psychosis is a loss of contact with reality that usually includes false beliefs or delusions, and seeing or hearing things that are not there.
Like a fever, psychosis is a symptom rather than a disease, and can be caused by a variety of triggers: exposure to mercury (the hats of the Mad Hatter were impregnated with the heavy metal), drugs like amphetamines, epilepsy, a brain tumor, dementia or psychiatric disorders like schizophrenia.
Psychosis Usually Involves Auditory Hallucinations
But unless psychosis is due to neurological causes, patients normally have auditory, rather than visual hallucinations.
"In terms of cinematography, it's much easier to portray the visual, " he said. "Whispers are not nearly as dramatic as seeing something."
Several risk factors may have made the fictional Nina susceptible to psychosis if she had a genetic vulnerability, said Lamberti.
"Natalie Portman's character was involved in a highly stressful competition, she had conflicted relationships with her mother and with her understudy, and she was the object of sexual advances by her director, " he said. "Any one of these issues alone would be stressful, but experiencing all of them at once could be emotionally devastating, particularly for a young woman who is somewhat naïve and sheltered."