Born in south London, Tilley worked for performance artist and club promoter Leigh Bowery as a cashier at his "Taboo" night club. Bowery introduced her to Lucian Freud in 1990 and she began posing for him the following year. During this time, she was also a full-time benefits supervisor at the Charing Cross jobcentre, a state-operated employment agency, and she eventually became manager there.
Freud painted several large nude portraits of Tilley, the first being Evening in the Studio (1993). Benefits Supervisor Sleeping, painted in 1995, was sold at auction in 2008 for £17 million ($33.6 million US) in New York City. In 2015, the 1994 painting Benefits Supervisor Resting sold for £35.8 million ($56.2million US). A fourth painting Sleeping by the Lion Carpet was painted in 1996. Freud also produced a number of etchings featuring Tilley, including Woman with an Arm Tattoo which Tilley sold in 2005.
In 1997, she published Leigh Bowery: The life and times of an Icon, a biography.
- "Leigh Bowery: The Life And Times Of An Icon By Sue Tilley Now Available As An Ebook From Open Road Integrated Media". Open Road Integrated Media.
- "The ballad of Big Sue". The Guardian. June 30, 2005.
- "'It's lovely,' says benefits supervisor whose portrait is set to sell for £17m". The Guardian. April 12, 2008.
- "Roman Abramovich 'revealed as Freud and Bacon buyer'". The Telegraph. May 18, 2008.
- "Freud's painting of a Jobcentre clerk breaks his record: 'Benefits Supervisor Resting' sells at auction for a staggering £35.8m". Daily Mail. May 14, 2015.
- "Great Works: Sleeping by the Lion Carpet 1995-6 (228.6cm x 121.3cm), Lucian Freud". Independent. July 28, 2011.
- "Freud tattoo model etching sold". BBC News. June 28, 2005.
- "Leigh Bowery: A life less ordinary". Independent. March 23, 2011.