As a junior elite gymnast, Mackie was the national champion on vault in 2001, and on vault, floor, and in the all-around in 2002. In 2003, she became the senior national all-around champion, as well as the Elite Canada champion on the uneven bars and balance beam. She was a member of the Canadian teams at the 2003 World Championships and at the 2002 and 2003 Pan American Games.