A standout age group swimmer in Omaha, Nebraska, Magee was born in Texas City, Texas. In 1975, at the age of 16, she joined the Dad's Club swim team under coach Skip Kinney. In high school she led Clear Lake to the 1976 state title with three gold medals and three state records. She was the first female swimmer in Texas to make an Olympic team in an individual event, swimming the 100-meter backstroke in Montreal in 1976. She was also a member of the 1977 world championship team and a four-time all-American at the University of North Carolina. Magee earned her undergraduate and law degrees from the University of Houston and has been a district attorney in Harris County since 1992.