Rice trained under Michael Bohl at St Peters Western Swimming Club. At the 2006 Commonwealth Games she won a surprise both the 200m individual medley, where she underbid their own record by 1.19 seconds in the finals, as well as gold over the 400 m of the same discipline. In the swimming world championships in 2007 in Melbourne, she won bronze over 200 m and 400 m medley. In both races she increased her personal best enormously and put new Australian records.
The Australian qualification competitions for the 2008 Olympic Games in Beijing she first broke the world record held by Katie Hoff over 400 m medley by 1.43 seconds, and put the new record on 4:31,46 seconds. Then they improved the world record of the Chinese Wu Yanyan over 200 m medley by nearly a second on 2:08,92 seconds. At the Olympic Games in Beijing in 2008, she won the gold in the 200m individual medley and 400 m layers, respectively before Kirsty Coventry. With the 4 × 200 m freestyle relay, she secured her third Olympic gold medal. In all three disciplines, it reached a new world record time.
Rice was until July 2008 for two years in a relationship with the Australian swimmer and world record holder Eamon Sullivan.