She is best known for her roles as bodybuilder Jackie in Love Lies Bleeding, Imperial communications officer Elia Kane in the second and third seasons of The Mandalorian, George in Syfy's zombie show Z Nation,[2] Major Sara Grey in The CW's superhero series Black Lightning, Kimball in Agents of S.H.I.E.L.D., and Jentorra in Ant-Man and the Wasp: Quantumania.

[3] O'Brian began studying martial arts at five years old, and at age nine earned her brown belt in Shorei Goju Ryu Karate.

[8] She obtained her personal trainer certification and began competing in bodybuilding figure competitions,[9] and training at the Indy Actors Academy.

[episode needed] In 2018, O'Brian booked her first regular role on the comedy action series Z Nation where she played George, a budding leader of the apocalypse.

In 2020, O'Brian was cast as Elia Kane, a key recurring character in Seasons 2 and 3 of the Star Wars series The Mandalorian.

[17] Shortly after moving to Los Angeles in 2016, O'Brian met her partner, Kylie Chi, on a student film project set.