Wallis comes from an artistic family environment; her father was an actor. The late actor Richard Harris was a maternal uncle. Wallis was born in England but spent much of her childhood in Portugal, where they went to school. She attended Saint Dominic's International School in Outeiro de Polima. She is fluent in Portuguese, French and Spanish.
In Portugal, she directed some short films. On her return to London Wallis worked professionally as an actress since 2002. Acting lessons she received from a private acting coach. She was in London initially worked as a commercial actress and appeared in independent films.
In 2005, she had, directed by Romesh Sharma, her first leading role in a feature film; she played the role of Sophie in the Bollywood film Dil Jo Bhi Kahey, a romantic love story between two students in Stockholm, an Indian and a French- Mauritierin. In 2007, she took over in the British television film Diana - the role of underwear models Kelly Fisher, who had an affair with Princess Diana's life companion Dodi Al -Fayed, the last 24 hours. A supporting role she played in the thriller The Man of Lies (2008) by Ridley Scott.
In 2009 she gave the role of Jane Seymour, the third wife of King Henry VIII of England, her debut in the British television series The Tudors. In 2010 she turned and directed by Madonna the movie WE, a romance about the love story between Edward VIII and Wallis Simpson.
Wallis lives in London.
- 2005: Dil Jo Bhi Kahey ...
- 2006: True True Lie
- 2007: Diana - The last 24 hours
- 2007: Butchered - Nobody can escape
- 2008: The Man Who Lies ( Body of Lies )
- 2009: The Ghost Town
- 2009: Right Hand Drive
- 2009-2010: The Tudors ( The Tudors )
- 2011: X - Men: First Class (X -Men: First Class )
- 2011: Pan Am