As she grew older, she would be punished for acts of disobedience or cruelty that she could not remember committing, she said. She would be baffled by a test in school that a different personality had prepared for. She never finished high school. According to her 1977 memoir, “I’m Eve,” written with a relative, Elen Sain Pittillo, she was scarred further by an early romance with a sadistic man, who beat her.  A severe headache would announce the emergence of a different personality. She began seeing Dr. Thigpen in Augusta, Ga., after her first marriage, when she began alternating between the demure and depressed Eve White and the self-indulgent party girl Eve Black, perplexing her husband with her bizarrely shifting behavior. In one episode depicted in the film, she wrapped the cord of a venetian blind around the neck of her young daughter, Taffy, when the child would not stop crying.  The personality Jane, a pleasant and sensible young woman, became manifest during her therapy. Her marriage ended. The second, to Don Sizemore, an electrician, began.  The two Eves and Jane proved evanescent, but as those personalities faded, others appeared, usually in groups of three. As doctors learned more about dissociation, the presumption that its main manifestation was multiple personalities with vastly different traits gave way to an understanding that the divides in a person’s identity could be far more subtle.  Even so, the way her divided self presented itself was remarkable; some of her personalities knew how to drive, for instance, but others did not. She opened a cloth store in Manassas, Va., her son said, “because one of the personalities was an accomplished seamstress.”  In the Post interview, Mrs. Sizemore said her personalities dressed differently, talked differently, ate differently.  “I once weighed 175 pounds because I was feeding three different people in the same body different meals,” she said.  Dr. Tsitos began treating her in 1970, and by 1974 she was no longer dissociating.  Attempts to reach Dr. Tsitos were unsuccessful, but another psychiatrist, Richard Kluft, who knew him as well as Mrs. Sizemore during his treatment of her, said in a phone interview that her previous therapy “had been all over the place and she felt betrayed.”  Dr. Tsitos, he said, “was a very savvy clinician who could see that more was going on than the typical picture of different personalities, that not all of them were apparent, and that the differences were sometimes very subtle.”  “Chris Sizemore was a lady,” Dr. Kluft said, “truly a beautiful human being. She did a lot of good. My hat’s off to Tony.”  Don Sizemore died in 1992. In addition to her son, a high school guidance counselor, Mrs. Sizemore is survived by two sisters, Louise Edwards, known as Tiny, and Becky Walton; her daughter, Taffy Fecteau; two grandchildren and three great-grandchildren.  Mrs. Sizemore wrote a follow-up to her memoir, “A Mind of My Own” (1989), in which she recounted the integration of her personalities and her life afterward. In later years she was a frequent speaker on behalf of people with mental illness and an accomplished figurative painter.  The actress Sissy Spacek attempted to buy the film rights to “A Mind of My Own,” but 20th Century Fox, the studio that produced “The Three Faces of Eve,” stood in the way, claiming it owned the rights to her life story in perpetuity. Mrs. Sizemore had earned $7,000 from the earlier movie; a settlement was reached with Fox, and the second movie was never made.  The sunny narrative of Mrs. Sizemore’s triumphant second act was called into some question in 2012, when Colin A. Ross, a psychiatrist specializing in dissociation, published a book, “The Rape of Eve,” in which he accused Dr. Thigpen of having exercised an unethical, Svengali-like influence over Mrs. Sizemore and manipulating her for nefarious purposes during and after his treatment of her ended. Dr. Thigpen died in 1999.  “At different times he functioned as her psychotherapist, publicist, literary agent, film agent, book editor, contracts negotiator and legal adviser,” Dr. Ross wrote. “He attended her husband’s funeral uninvited, was her son’s godfather and engaged in sexual misconduct with her. He arranged for her to have an abortion, and during the procedure she was sterilized without her or her husband’s consent.”  Dr. Ross and Mrs. Sizemore had worked together on a documentary film about dissociation. In a phone interview, he said she had been a collaborator on the book, which portrayed her as still under Dr. Thigpen’s control in some ways until his death.  “I want to give Dr. Thigpen and Dr. Cleckley their due, because they were the first to diagnose Mom,” Bobby Sizemore said in response to a question about Dr. Ross’s assertions. Mr. Sizemore knew about Dr. Ross’s book but had not read it, he said, adding that, yes, his mother had participated in it.  “There is some truth there,” he said.  A version of this article appears in print on August 7, 2016, on page A20 of the New York edition with the headline: Chris C. Sizemore, Real ‘Three Faces of Eve,’ Dies at 89. Order Reprints| Today's Paper|Subscribe
The woman whose story of dissociative identity disorder was made into the 1957 Oscar-winning movie was eventually treated and became a mental health advocate.