Billie's film roles span throughout her eventful career starting with a small part in 1996's Evita and The Leading Man but her first credited role was in 2004 where she played opposite Orlando Bloom in The Calcium Kid. In 2005 Billie played the part of Vicky in Things To Do Before You're 30 and the main role of Jenny in British horror Spirit Trap. 2010 saw Billie voice Bonnie in Animals United and an adaptation of The Raven.
November 2013 was a big occasion for many fans as Doctor Who celebrated its 50th anniversary. As part of the celebrations, Billie returned to feature in the 3D special, The Day of the Doctor. The film, which was also released in more than 1,500 cinemas worldwide, sold out in under an hour becoming one of the single fastest selling live events in cinema history.
Hot off the Young Vic's stage, in 2016, Billie starred in the acclaimed City of Tiny Lights, a gritty thriller based in London.