She is also known for her roles as Kim Fischer in The Mentalist (2013–2014), Amara / The Darkness in Supernatural (2015–2020), Lisa Ţepeş in Castlevania (2017–2021), and Puck in Pac-Man: Circle (2024).

[1] Swallow started her career in theatre, where she performed in various productions, including the Broadway musical High Fidelity, King Lear, The Taming of the Shrew, A Midsummer Night's Dream, Cat on a Hot Tin Roof at the Guthrie Theater, Much Ado About Nothing for Shakespeare in the Park, and the world-premiere of off-Broadway shows Romantic Poetry and Measure for Pleasure.

She starred in world premieres of Donald Margulies' play The Country House at Los Angeles' Geffen Playhouse, opposite Mark Rylance in Louis Jenkins' play Nice Fish at the Guthrie Theatre,[4] and in John Patrick Shanley's musical Romantic Poetry at Manhattan Theater Club.

[7] The show centers on the comic misadventures of the duo as they navigate very different life challenges with varying degrees of sanity and dignity.

[8] Swallow's first television role was in Guiding Light, and she later played parts in Southland, Ringer, The Good Wife, NCIS, Flight of the Conchords, Medium, as series regular Dr. Michelle Robidaux on TNT's medical drama Monday Mornings[2] and Rizzoli & Isles.