Montgomery began her acting career at the age of 12, when she appeared on British children show Short Change, with her brother Jason. In 2008, she was cast as the love interest of Nicholas Hoult in an episode of the teen drama Skins. Montgomery appeared in both the critically acclaimed Dis/Connect and short film Flushed. After a few years of living in London, she moved to Los Angeles so she could chase the dreams she had as a child.