She began her career as a child actress and first gained prominence through her roles in the BBC dramas Five Daughters (2010) and Dive (2010), the play Spur of the Moment, and the film Death of a Superhero (2011).

Loftus was born in Nottingham to Irish parents Paddy and Eileen[2] from Drumcondra, Dublin and Roscrea, County Tipperary;[3] she has an older sister Aoife.

[2] Throughout her childhood she visited family in Ireland for holidays, in Dublin, Tipperary, Cork, Kerry, Galway and Clare.

"[9] That same year, Loftus made her London stage debut as Leonie Fowler in Spur of the Moment by Anya Reiss at the Royal Court Theatre.

[3] In 2013, Loftus began starring as Agnes Towler in the ITV period drama Mr. Selfridge,[2] a role she would play for the first three series.

In 2016, she played Sonya Rostova in the BBC adaptation of War & Peace,[2] and appeared in the films Pride & Prejudice & Zombies and Property of the State.

[13] In 2017, she played Joan in the 40th anniversary production of Stephen Lowe's Touched at Nottingham Playhouse alongside fellow Television Workshop alumni.