Duke started her amateur career in 2010. She fought mainly for Absolute Action MMA and Tuff-N-Uff. She obtained the amateur featherweight title in both organizations.
In 2012, Duke moved to professional mixed martial arts and signed with Invicta FC.
Duke made her professional and promotional debut against Suzie Montero on July 28, 2012 at Invicta FC 2. She won via TKO in the third round.
Duke faced Marciea Allen on October 6, 2012 at Invicta FC 3. She won via submission due to an armbar in the first round. This victory earned her a submission of the night bonus award, which was split between Duke and Stephanie Frausto, due to her submission victory over Amy Davis in the same event.
Duke faced Miriam Nakamoto on April 5, 2013 at Invicta FC 5. The result was originally a KO victory for Nakamoto, but was later overturned by the Missouri Office of Athletics to no contest due to an illegal knee.
In August 2013, Duke was announced as a cast member of The Ultimate Fighter: Team Rousey vs. Team Tate. She defeated Laura Howarth via submission due to a triangle choke during the entry round and was the second female pick of Team Rousey.
Duke faced Raquel Pennington in the elimination round. Pennington defeated Duke via unanimous decision (29-28, 29-28, 29-28) and the performance earned both participants Fight of The Season honors.
Duke made her promotional debut against TUF 18 teammate Peggy Morgan on November 30, 2013 at The Ultimate Fighter 18 Finale. She won via unanimous decision (30-27, 30-27, 30-27).
In her second UFC fight, Duke faced Bethe Correia at UFC 172. She lost the fight via unanimous decision (30-27, 29-28, 30-27).
Duke faced Leslie Smith at UFC Fight Night: Cerrone vs. Miller on July 16, 2014. She lost the fight via TKO early in the first round after taking several punches to the face and body.
Duke faced Elizabeth Phillips at UFC on Fox 16 on July 25, 2015 in a rematch of their amateur bout at RFA 2 - Yvel vs. Alexander. Duke lost the fight via unanimous decision and was subsequently released from the promotion.
Duke is a self-confessed gamer; in an interview, Ronda Rousey claimed that Duke "pays more of her bills streaming than she does from fighting".