After being introduced to bobsleigh in 2010, O’Brien competed at the 2013 FIBT World Championships with pilot Jenny Ciochetti, but a torn hamstring took her out of the first half of the Olympic season and she missed qualifying as a bobsleigh brakeman for the 2014 Winter Olympics. She decided to try piloting a bobsled and attended driving school in Calgary in March 2014. At the same time, there was a testing camp for Cycling Canada at the Canadian Sport Institute. Having scored good test results, she was competing internationally within months. In September, she debuted at the Pan American Championships, finishing fifth in both the team sprint (with Monique Sullivan) and the keirin. O’Brien split 2014-15 between track cycling and bobsleigh, competing on both World Cup circuits as well as at both world championships. At the 2015 UCI Track Cycling World Championships, she and Sullivan finished twelfth in the women's team sprint. In June 2015, she broke the 200 m time trial record that stood for 19 years at the Lehigh Valley Preferred Cycling Center in Trexlertown, Pennsylvania. By the following month, O'Brien and Sullivan set a track record to capture the women's sprint title at the 2015 Pan American Games in Toronto. Moreover, she managed to add a silver to her Pan American Games career tally in the individual sprint race, with the gold going to her teammate Sullivan.