She made her Broadway debut in the 1948 revueSmall Wonder, directed by Burt Shevelove and choreographed by Gower Champion and co-starring Tom Ewell, Alice Pearce and Jack Cassidy. She appeared in the 1950 comedy Season in the Sun, written by The New Yorker magazine's theatre critic, Wolcott Gibbs. Diener met her future husband, theatre directorAlbert Marre in 1953, when she won the role of Lalume, the seductive wife of the Wazir, in Kismet, winning a Theatre World Award for her performance. They were married three years later and subsequently had a son Adam and a daughter Jennifer. She reprised the role of Lalume in Kismet in London's West End alongside Alfred Drake and Doretta Morrow, who had all starred in the original Broadway production. In 1958, Marre directed a production of At the Grand, a musical adaptation of Vicki Baum's 1930 novel Grand Hotel, in Los Angeles with Diener as an operadiva who falls in love with a charming, but larcenous, faux baron. Mitch Leigh's Man of La Mancha also was directed by Marre, who cast his wife as Aldonza, the lusty serving wench envisioned by the deranged Don Quixote as virtuous Dulcinea. She appeared in the production Off-Broadway at the ANTA Theatre, opening on November 22, 1965, and then when the musical opened on Broadway at the Martin Beck Theatre on March 20, 1968. The critics were unanimous in praising her portrayal, but she was overlooked by the Tony nominations committee. She went on to play the role in London and Amsterdam, in Paris and Brussels in French. She appears on the cast recording with Brel, L'Homme de la Mancha. At age 62, she took over the same role she had created decades earlier in the 1992 Broadway revival starring Raúl Juliá when Sheena Easton collapsed during one performance and Diener filled in for the second half of the show. Diener reunited with Leigh as composer and Marre as director for both Cry for Us All, which closed after nine performances, and Home Sweet Homer, which closed on opening night, despite the presence of Yul Brynner as Odysseus. Diener's most famous stage roles went to others when they reached the screen - Dolores Gray in Kismet and Sophia Loren in La Mancha - and she never had a film career of her own. In addition to appearing on Broadway and in London's West End, she performed in nightclubs, such as the Blue Angel in Manhattan, early television, and in regional theatre.
