When she was a teenager, McKeon played Aisling O'Brien in the
RTÉ soap opera
Fair City from 2004 to 2007. After graduating from Trinity, McKeon went into theatre. She starred as Dorothy in Sean Gilligan's
The Wizard of Oz. In 2012, she played
Cinderella in the
Gaiety Theatre's Christmas pantomime as well as Philomena O'Shea in the
Improbable Frequency revival. She also appeared in
The Life and Sort of Death of Eric Argyle at the
Pleasance Dome in Edinburgh and
Anglo: The Musical at the
Olympia Theatre. McKeon then relocated to London when she was cast as Natalie in
The Commitments at the
Palace Theatre, originating the role and marking her
West End debut in 2013. She was then a lead vocalist in
Kyle Riabko's
Bacharach Reimagined shows in 2015; ''What's It All About?
was put on at the Menier Chocolate Factory. It was reimagined as Close to You
when it moved to the Criterion Theatre. She took over the role of Cynthia Weil in Beautiful: The Carole King Musical'' for its final ten weeks at the
Aldwych Theatre in 2017. In 2019, McKeon was cast as
Princess Anna opposite
Samantha Barks as
Elsa in the West End run of the stage adaptation of
Disney's
Frozen. After being delayed due to the
COVID-19 pandemic, the show opened in 2021 at the
Theatre Royal, Drury Lane. For her performance, McKeon was nominated for both the
WhatsOnStage Award and the
Laurence Olivier Award for Best Actress in a Musical. McKeon released an EP
Here I Go (2021) consisting of musical theatre covers. ==Personal life==