The story of All About Eve originated in an anecdote related to Mary Orr by actress Elisabeth Bergner. While performing in The Two Mrs. Carrolls during 1943 and 1944, Bergner allowed a young fan, Martina Lawrence, to become part of her household and employed her as an assistant, but later regretted her generosity when the woman attempted to undermine her. Referring to her only as "the terrible girl," Bergner related the events to Orr, who used it as the basis for her short story "The Wisdom of Eve" (1946). In the story, Orr gives the girl a more ruthless character and allows her to succeed in stealing the older actress' career. Bergner later confirmed the basis of the story in her autobiography Bewundert viel, und viel gescholten (Greatly Admired and Greatly Scolded).  In 1949, Mankiewicz was considering a story about an aging actress and, upon reading "The Wisdom of Eve," felt the conniving girl would be a useful added element. He sent a memo to Darryl F. Zanuck saying it "fits in with an original idea [of mine] and can be combined. Superb starring role for Susan Hayward." Mankiewicz presented a film treatment of the combined stories under the title Best Performance. He changed the main character's name from Margola Cranston to Margo Channing and retained several of Orr's characters -- Eve Harrington, Lloyd and Karen Richards, and Miss Casswell -- while removing Margo Channing's husband completely and replacing him with a new character, Bill Sampson. The intention was to depict Channing in a new relationship and allow Eve Harrington to threaten both Channing's professional and personal lives. Mankiewicz also added the characters Addison DeWitt, Birdie Coonan, Max Fabian, and Phoebe.  Zanuck was enthusiastic and provided numerous suggestions for improving the screenplay. In some sections, he felt Mankiewicz's writing lacked subtlety or provided excessive detail. He suggested diluting Birdie Coonan's jealousy of Eve so the audience would not recognize Eve as a villain until much later in the story. Zanuck reduced the screenplay by about 50 pages and chose the title All About Eve from the opening scenes in which Addison DeWitt says he will soon tell "more of Eve ... All about Eve, in fact."

Answer this question "when was all about eve developed?" by extracting the answer from the text above.
The story of All About Eve originated in an anecdote related to Mary Orr by actress Elisabeth Bergner.