At the age of five, Kemper moved with her family to St. Louis, Missouri, where she attended Conway Elementary School. She later enrolled at John Burroughs School, a private prep school where her interest in performance and improvisational comedy was sparked. One of her teachers at the time was actor Jon Hamm, known for his role in the television series Mad Men.

She continued her education at Princeton University, where she initially played on the field hockey team before shifting her focus to theater. During her time at Princeton, she joined the improvisational comedy group Quipfire! and the musical theater troupe Princeton Triangle Club. She graduated in 2002 with a degree in English. Kemper pursued further studies in English at the University of Oxford's Worcester College.

Early Career and Breakthrough Roles

Kemper began her professional acting career with a commercial for Kmart, which earned her a Screen Actors Guild card. In the commercial, she played a woman camping with her husband. In the early 2000s, she appeared in sketch segments on Late Night with Conan O’Brien and had guest appearances on shows like The Gastineau Girls and Important Things with Demetri Martin, which helped her gain visibility in the comedy scene.

After moving to New York City, Kemper became active in the local theater community and performed regularly at the Upright Citizens Brigade Theatre. She gained further exposure through her appearances in online comedy videos, including sketches for the humor website CollegeHumor.