McMillan qualified for the 2012 London Olympics at the U.S. Olympic trials on June 30, 2012. She placed third at the trials with a score of 6188 points. At the trials, McMillan set personal bests in 100 meter hurdles, 200 meters, shot put, javelin, and 800 meters and achieved the Olympic A standard. At the 2012 Olympics, she finished in 28th place.