 A native of San Diego, California, she was trained by coach Dave Salo of the Irvine Novaquatics from the age of 12.She broke the USA's 11-12 age-group national record at age 12 in 50 yard backstroke, and at the age of 14, MacManus attempted to make the U.S. Olympic team in the 100m backstroke, finishing in fourth place in the U.S. Olympic trials.At the Brazil meet of 2001–2002 FINA Swimming World Cup, she won both the 50 and 100 backstrokes.