Overholt attended the 2013 Canada Games representing British Columbia as a 15-year-old competitor. There she won gold in the individual 200 m and 400 m medleys while adding a gold and a silver in the 400 m and 200 m freestyle respectively. She next won a bronze medal in the 400 m individual medley at the 2013 FINA World Junior Swimming Championships. Overholt's first major competitive podium finish came in Glasgow, Scotland as part of the 4×200 m freestyle relay at the 2014 Commonwealth Games, where she competed as a sixteen-year-old and helped the relay team win a silver medal. She also anchored the team that won a bronze medal in the 2014 Pan Pacific Swimming Championships.