[5] Spencer made her acting debut at the age of 12 as Jane Banks in Richard Eyre's 2004 production of the musical Mary Poppins.

[8] In 2013, Eyre again cast her, this time as Christine Keeler, in the Andrew Lloyd Webber musical Stephen Ward, with Charlotte Blackledge as Mandy Rice-Davies.

[5] After her theatre appearance as Christine Keeler ended, Spencer had a small part in Line of Duty and then was cast by the same director as the jockey Tina Fallon in the 2014 E4 television series Glue.

[14] She played the lead role, Lilly, in the film Bypass with George MacKay[6] and appeared as Ellie in the BBC2 television series Stonemouth.

[16] In the BBC1 horror television series The Living and the Dead, broadcast in June 2016, she played the role of Charlotte Appelby, a photographer turned housewife, with Colin Morgan.

[20] Spencer will also play[needs update] a hapless youth in the teen horror film Gateway, which uses the Momo Challenge as a plot device.