Kirk was born in 1978 to an associate accounting professor and an assistant economics professor. Her father later died sometime in her life. After graduating from the University of Southern California, she began a writing career, becoming a staff writer for Without a Trace and also writing episodes for Criminal Minds, Cold Case, and Made in Jersey. In 2007, Kirk married Ben Fritz, a writer for the video-game and new-media sections for Variety magazine.
Kirk has written the following episodes for Criminal Minds: