Miller is best known for originating the role of disco diva wannabe Deloris Van Cartier in the 2009 West End and 2011 Broadway productions of Sister Act. She also starred as the Leading Player in the 2013 revival of Pippin. This role earned her a Tony Award for Best Actress in a Musical.
She is also known for her role as Commander Paylor in The Hunger Games: Mockingjay films, and her starring role as Daisy Grant in the CBS political drama Madam Secretary.
On June 14, 2014, Miller married venture capitalist David Mars in New York City. Robin Burch, Miller’s mother, who is a Baptist minister, officiated at the ceremony. Their daughter, Emerson Harper, was born on August 9, 2017 in New York City.