She received critical acclaim for her portrayal of a woman on the run[2][3] in Steve Rodgers' play Savage River[4] for the Griffin Theatre Company.
Sergeant received praise as "a stand out performance amid an excellent cast" in Sue Smith's Thrall.
[5] She was cast as Nina Cruz in the Melbourne Theatre Company production of All About My Mother, an adaptation for the stage based on the film by Pedro Almodóvar, directed by Simon Phillips.
In 2012 she starred in Iron Sky, as Vivian Wagner, a campaign adviser to a Sarah Palin-like president of the United States, who later becomes general on the US' interplanetary warship USS George W.
In 2014 she played the Jabberwocky in Once Upon a Time in Wonderland and Francesca Guerrera in The Originals.