Cain ran for 10 seasons for Bronxville High School, winning numerous state titles, as well as two national titles while still a Bronxville athlete. In 2010, she was the NYS Class C Cross Country Champion; in 2011, she was both NYS Class C and NYS Federation Champion. She ran the 800 meters at the 2012 United States Olympic Trials and placed 18th, and also ran at the 2012 World Junior Championships in Athletics, where she broke the American high school girl's outdoor record in the 1500 m with a 4:11.01, surpassing the record of Jordan Hasay in the 2008 United States Olympic Trials by over 3 seconds. The effort qualified her to run in the World Championships. She had taken second in the same event the year before.