She participated at the 2008 IIHF World Women's U18 Championship in Calgary and was Canada's leading scorer. In a January 9, 2008 contest versus Germany (contested at the inaugural World Women's Under-18 hockey championship), Poulin notched one goal and two assists in a 10–1 win. She was part of the team that won a silver medal. She finished the tournament with eight goals and six assists in five games. In two seasons with Canada's national women's under-18 team, Poulin became the all-time leading scorer in U18 team history with 31 points in 17 games. She helped Canada to back-to-back silver medals at the IIHF World Women's Under-18 Championship in 2008 and 2009.