Judge Kelly received her Bachelor of Arts degree summa cum laude in 1987 from Duke University. She received her Juris Doctorate cum laude in 1991 from Harvard Law School. In 1991, she was a law clerk to Judge Donald J. Porter of the United States District Court for the District of South Dakota. She then was a clerk to Judge David R. Hansen of the United States Court of Appeals for the Eighth Circuit. After working as a visiting instructor at the University of Illinois College of Law, she became an Assistant Federal Public Defender in the Northern District of Iowa in 1994, serving as Supervising Attorney in the Cedar Rapids office from 1999 to 2013.

President Barack Obama signed her commission as Circuit Judge for the United States Court of Appeals for the Eighth Circuit on April 25, 2013.