Hassett made her senior Football Ferns debut in a 1–0 win over Argentina on 16 June 2008. She played in Germany at the 2011 FIFA Women's World Cup with New Zealand, seeing time in all three games. In 2012, she represented her country at the London Olympics, helping the Football Ferns become the first New Zealand team to advance to the second round in a major FIFA tournament. She played in all four games with three starts. Hassett featured in all three of New Zealand's matches at the 2015 FIFA Women's World Cup in Canada. She also featured in all three of New Zealand's matches at the 2016 Olympics. On 24 July 2021, Hassett scored one goal in New Zealand's 1-6 loss against the United States in 2020 Olympics.