She joined the National Youth Theatre at 17, where she made her breakthrough stage role in Immaculate Conceit, a play about a stripper who is pregnant with the next messiah. She then found small roles in television, before joining Kevin Spacey's Old Vic, New Voices collective for a year in 2005. She was delighted to be part of the collective of actors taking part in the 24-hour plays at The Old Vic. The group received its name because Spacey, who selected the actors, believed them to be the best new actors around.
After a five-month tour of India performing Shakespeare's A Midsummer Night's Dream in Jaipur in 2006, she returned to Britain, but endured a lean year and nearly gave up acting altogether when she landed the role of Jill Mason in her West End debut in Equus at the Gielgud Theatre. She beat over 300 other actresses to the role opposite Harry Potter star Daniel Radcliffe in Thea Sharrock's high-profile revival of Peter Shaffer's award-winning play.
Christie's mother, Sue, in addition to conducting for the Millhouse Green Male Voice choir in Penistone, sings with The Mastersingers. Her father Paul, who died in 2012, was a property developer. Her brother Luke is also a musician, singer, and Songwriter. The pair have a band together called Luke J Christie & The Held Breath. She was inspired by her parents, who taught her that she "could do anything [she] wanted in life and to always be [her]self and follow [her] own path." She has been highly influenced by her parents her whole life. "I owe all my success to my parents for giving me the opportunities to get to this point in my career and I would like to pay tribute to them...I'm just so grateful to my mum for giving me the gift of music and to both her and my dad for always supporting and encouraging me," she explained in a 2013 interview with the Huddersfield Daily Examiner.
On 20 April 2014, she collaborated with her Once cast members and contributed her piano and vocal talents for a live-album recording of the Adam Brown and Friends performance at the Bowery Poetry Club.
