She competed at the 2008 World Junior Championships in the 1500m. She did not advance past the first heat, finishing with a time of 4:26.28. In the European U23 Championships in Lithuania, Treacy placed 18th in the 1500m. In the following year's European U23 Championships she set a personal best time in the first heat of 4:16.32, which qualified her for the finals. Out of the 12 finalists, she finished 10th with a time of 4:25.97. She was later moved up to ninth place when Yelena Arzhakova was disqualified.