McGrath originally sought to work in fashion journalism and took on a job at Image magazine[1] before becoming a wardrobe assistant on the set of The Tudors.

[8] Emilia Fox portrayed Elizabeth II in the same episode in which McGrath appeared; the two had previously worked together as sisters Morgause and Morgana in Merlin.

[9] In 2011, McGrath appeared with Roger Moore in the comedy-drama film A Princess for Christmas, a Hallmark Channel Original Movie shot mainly at the Peleş Castle in Romania.

[12] McGrath was reunited with her The Tudors co-star and close friend Jonathan Rhys Meyers in NBC and Sky Living's horror drama TV series Dracula; she portrayed Lucy Westenra.

[17] McGrath portrayed the lead role in the first season of Chiller's original horror series Slasher, which premiered on 4 March 2016.

[19][20] She debuted in the season two premiere episode titled "The Adventures of Supergirl" and was promoted to a series regular in March 2017 and maintained this role until the show's end in 2021.