[2] Grainger attended Parrs Wood High School from 1999 to 2006,[3] and in 2007 began study for a degree in English literature at the University of Leeds.

[2] Grainger's first acting role was at five years old in the BBC comedy drama series All Quiet on the Preston Front.

Grainger played Megan Boothe in Where the Heart Is, Stacey Appleyard in Waterloo Road and Sophia in Merlin.

[5] After her role as Emily in the film The Scouting Book for Boys (2009),[6] she played one of the Rivers sisters opposite Mia Wasikowska and Michael Fassbender in Cary Fukunaga's 2011 retelling of Jane Eyre, and had a minor role in Bel Ami alongside Robert Pattinson and Uma Thurman.

In June 2011, she was cast in the leading role of Estella in Mike Newell's film adaptation of Great Expectations, opposite Jeremy Irvine and Helena Bonham Carter.

She was one of the female leads in the 2014 film The Riot Club, adapted from the play Posh, alongside Max Irons.

It is inspired by primary accounts of refugees, and is part of UNHCR's #WithRefugees campaign, which also includes a petition to governments to expand asylum to provide further shelter, integrating job opportunities, and education.