Passey graduated from the Bridge Drama School in London.[3] Passey first started her career in the BBCdocumentary filmThe Last Flight to Kuwait in 2007 opposite Freddie Stroma.[4][5] Later in 2011, she starred in the British drama film, A Landscape of Lies, as well as the 2012 film Saint Dracula 3D.[6] In 2014, Passey appeared in The Smoke, which was released on 20 October 2014.[7]
On 21 November 2012, Passey started playing the role of Sienna Blake in the Channel 4 soap opera Hollyoaks. Emily Lawrence was initially cast in the role, before Passey replaced her.[8][9] Tina Campbell of the Metro praised Passey's portrayal and described Sienna as having various layers to her personality. She noted that a backstory consisting of a woman beating father, unhinged mother and long-lost brother left her normality doomed. She added that "despite her (many) flaws, you can’t help but love Sienna" and deemed her Hollyoaks' best character.[10] Katie Archer of BT described Sienna as appearing "sweet and innocent", but "on the inside, things are far uglier."[11]MSN.com labeled the character a "barmaid [turned] psychopath".[12] Viewers' perception of Sienna changed during her tenure. Passey told an Inside Soap reporter that Sienna gained sympathy following revelations about her long-lost daughter.[13] For her role as Sienna, Passey won the Villain of the Year award at the 2014 British Soap Awards.[14] She was nominated for Most Popular Newcomer at the 2014 National Television Awards, later receiving numerous nominations in the Serial Drama Performance category.[15][16] Then in 2017 and 2018, she was nominated for Best Actress at the British Soap Awards.[17] In 2019, alongside her role in Hollyoaks, Passey appeared in the Netflix series Free Rein, in the recurring role of Felicite.[18]
