In March 2007, 15-year–old Duggan came off the substitute's bench to score on her debut for England Under–17s. She has since represented England at Under–19, Under–20 and Under–23 levels. She played in the FIFA U-20 Women's World Cup in both 2008 and 2010. On Duggan's 18th birthday, she scored one of the two goals in England's 2009 UEFA Women's Under-19 Championship maiden final win, against Sweden in Belarus.