[4] Diamond made her professional debut in the musical television special of Jesus Christ Superstar Live in Concert on NBC as a featured member of the ensemble.

[citation needed] In 2019, Diamond originated the roles of Lindy and Dorothy in the world premiere of Ethan Coen's A Play Is a Poem at Los Angeles' Mark Taper Forum.

[14] Diamond also originated the roles of Young Tori and Amelia in Williamstown Theatre Festival's world premiere production of Row which opened on July 17, 2021.

[16][17] Following their sold-out run at New York City Center, a limited Broadway transfer was announced on January 10, 2023, with Diamond and Platt continuing their roles as Lucille and Leo Frank.

[19] Diamond originated and received acclaim for the role of Fritz, a covert revolutionary, in the 2023 Off-Broadway world premiere of Stephen Sondheim's final musical, Here We Are, an adaptation of two Luis Buñuel films.