In September, she debuted at the Pan American Championships, finishing fifth in both the team sprint (with Monique Sullivan) and the keirin.

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.

[3] 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.

[11][12] In the 2022 World Para Cycling Track Championship in Saint-Quentin-en-Yvelines, France, she won a silver medal in C4 500 metres time trial.