Wilde was born in Basingstoke, Hampshire, England. She is descended from the aristocratic Gough-Calthorpe family. Her father, John Anstruther-Gough-Calthorpe, is the grandson of Sir Fitzroy Anstruther-Gough-Calthorpe, 1st Baronet.
Her maternal grandmother's parents were peers Bernard Fitzalan-Howard, 3rd Baron Howard of Glossop and Mona Fitzalan-Howard, 11th Baroness Beaumont.
Wilde has a younger sister, Octavia, as well as five half-siblings: Olivia and Arabella Llewellyn, from her mother's first marriage, and Georgiana, Isabella, and Jacobi, from her father's first marriage, to Lady Mary-Gaye Curzon.
Wilde attended Heathfield St Mary's School, Ascot and St Swithun's School, Winchester, before leaving to pursue a course in art while continuing with her modelling career. She then studied fine art at the City and Guilds of London Art School but left to pursue acting.
Wilde began her career as a model and appeared in campaigns for L.K.Bennett, Burberry and Topshop. She also appeared in magazines such as InStyle, Cosmopolitan and Vogue.
In 2007, she was named the second-most-eligible girl in Britain but rejected press attention and the "It girl" label. She did not do her first interview until 2008, when she said: "I don't understand why I got anywhere near such a list because I have done nothing to help it. It's the same with my sister Isabella – we both avoid the society thing."
In December 2009, Wilde made her acting debut in the adventure comedy film St Trinian's 2: The Legend of Fritton's Gold. In May 2010, Wilde appeared in an episode of the BBC television series Doctor Who.
In December 2010, she made her film debut in the adventure film The Three Musketeers, an adaptation of the novel of the same name and portrayed the role of the queen's lady-in-waiting Constance Bonacieux.
In 2014, she starred in the remake of Endless Love, opposite Alex Pettyfer.
Wilde married Alan Pownall in 2014, and has two children with him.