In 1999, Hemingway became the deputy staff director of the United States House Committee on Oversight and Reform. In 2001 and 2002, she was the associate director of public affairs at the United States Department of Transportation. She was the director of legislative and regulatory affairs at the Blue Cross Blue Shield Association before becoming a staffer of the United States Senate Committee on Homeland Security and Governmental Affairs. After eight years with the Homeland Security Committee, Hemingway worked as the treasurer of the District of Columbia Library Association and president of the Junior League of Washington. She returned to the United States House Committee on Oversight and Reform in 2015. In 2017 and 2018, she was the director of operations for then-Speaker Paul Ryan. Hemingway was selected to serve as deputy Sergeant at Arms of the United States Senate in December 2018.
