Training at Kingscliff, New South Wales, Calub, first gained international selection after winning the 100 m and 200 m backstroke at the 2000 Australian Championships. At the Olympics, she combined with Leisel Jones, Susie O'Neill and Petria Thomas to register a silver medal in the 4 × 100 m medley relay, trailing the Americans home by 3s. In her individual events, Calub came seventh in the 100 m backstroke and was eliminated in the heats of the 200m backstroke.
In 2001 at the 2001 World Aquatics Championships, Calub combined with Jones, Thomas and Sarah Ryan to win the 4 × 100 m medley relay, the first time that Australia had defeated the United States in the event at international competition. This was repeated at the 2002 Pan Pacific Swimming Championships in Yokohama, where she combined with Jones, Thomas and Jodie Henry. She also won two golds and a silver at the 2002 Commonwealth Games in Manchester. She retired at the end of 2002. She also won a silver in the 100 m backstroke at the Pan Pacific Championships, behind Natalie Coughlin.