[5] She was the standby for Elphaba in the Broadway production of Wicked, and originated the role of Martha Bessell in Spring Awakening.

[6] She also played Hélène Kuragina in the American Repertory Theatre production of Natasha, Pierre & The Great Comet of 1812 in 2015.

She originated the role of Sandy Cheeks in the Broadway production of SpongeBob SquarePants, which opened on December 4, 2017.

[7] In September 2018, Cooper played Julie Nichols in the musical adaptation of the 1982 film Tootsie in its Chicago debut and reprised the role on Broadway in spring 2019, receiving a nomination for a Tony Award for Best Actress in a Featured Role in a Musical for her performance.

Also in 2022, she took part in the HBO documentary film Spring Awakening: Those You've Known, which saw the 15 year reunion of the original cast of the musical.