Miller was cast as the lead role of Delores Van Cartier in Sister Act, a role she had understudied for six months during its initial run in the United States, following a year-long international search. The London production opened on June 2, 2009 at the London Palladium, and although it received mixed reviews, most critics singled out Miller and praised her performance. Benedict Nightingale of The Times cited her "terrific voice" and continued, "Add warmth, humour, vivacity—and you've a star who lacks Whoopi's wry vulnerability but adds dazzle to the razzle around her," while David Benedict of Variety thought her "powerhouse vocals, pitched somewhere between Gloria Gaynor and Whitney Houston, and her thrillingly fast vibrato act as the show's engine." For this role Miller won the whatsonstage.com Theatregoers Choice Award for Best Actress in a Musical and was also nominated for the Laurence Olivier Award for Best Actress in a Musical. She remained with the production till it closed on October 30, 2010.