She is best known for her work on Broadway and for originating the role of Cady Heron in the 2018 Tony-nominated musical Mean Girls, for which she received an Outer Critics Circle Award nomination.

[4] At the age of seven, her interest in theatre was piqued after reading the Jack Prelutsky poem "The Turkey Shot out of the Oven" and hearing the audience's positive response to her performance.

[6][19] She left the production along with fellow Les Misérables co-stars Ramin Karimloo and Samantha Hill on August 30, 2015, and was replaced by Memphis star Montego Glover.

[20] In the summer of 2016, Henningsen portrayed Ensign Nellie Forbush, opposite Ben Davis, in the Pittsburgh Civic Light Opera's production of South Pacific.

[21][22] In February 2017, she appeared in an Off-Broadway staged concert of Jerry Herman's musical Dear World as Nina with York Theatre, starring alongside Tyne Daly, Alison Fraser, and Ann Harada.

[23][24] Henningsen returned to the Pittsburgh Civic Light Opera (PCLO) in the summer of 2017, starring as Sophie in the company's regional production of Mamma Mia!.

[36] In January 2020, it was announced that Henningsen would be joining the Broadway cast of the new musical Flying Over Sunset, scheduled to open in the spring of 2020 at the Vivian Beaumont Theater under the direction of James Lapine.

[46][47] Henningsen has actively been involved with Sing For Hope, a NYC-based non-profit organization dedicated to creating access to high-quality arts education and programming throughout New York City.

[48][49] She serves as an artist partner, teaches classes, and leads workshops with purpose of introducing and encouraging creative expression in NYC children with decreased access to the arts.

[55] In December 2018, Henningsen participated in the second annual Broadway Beats Hunger concert, raising funds for the Summit Medical Group Foundation's "Food, Health and Hope: An Answer to Diabetes" initiative.