Lilly attended Wilton High School in Wilton, Connecticut. While still attending high school, Lilly became a member of the United States women's national team. She was recruited by, and eventually chose to attend, the University of North Carolina at Chapel Hill.Lilly competed as a student-athlete, playing for the university's North Carolina Tar Heels women's soccer team from 1989 to 1992. During her time there, she won the NCAA Women's Soccer Championship every year she played. She won the Hermann Trophy as a junior in 1991 To honor her time with the school, North Carolina retired her #15 jersey in 1994.Lilly grew up in Wilton, Connecticut and lives in Needham, Massachusetts. She is married to Brookline fireman David Heavey, a former hockey and golf star at the University of Connecticut. Lilly gave birth to her first daughter Sidney Marie Heavey on her birthday, July 22, 2008, and her second daughter Jordan Mary Heavey on September 2, 2011.
She appeared in the HBO documentary Dare to Dream: The Story of the U.S. Women's Soccer Team. Lilly helps run a soccer camp with Mia Hamm and Tisha Venturini-Hoch.
Lilly made her debut for the United States women's national soccer team in 1987, when she was still attending high school. During her international career, she surpassed the previous women's world record of 151 caps, held by Norway's Heidi Store, on May 21, 1998.On January 30, 1999, she surpassed what was then the men's record of 164 caps, held by Adnan Al-Talyani of the United Arab Emirates.Lilly has participated in the 1991, 1995, 1999, 2003, and 2007 editions of the FIFA Women's World Cup. She is a two-time World Cup champion, winning in 1991 and 1999. When she played against North Korea on September 11, 2007, in the 2007 FIFA Women's World Cup, she became the first woman (and only the third player overall) to participate in five different World Cup Finals; by scoring a goal against England on September 22, 2007, she became the oldest woman to score in the World Cup.Lilly has also competed in the 1996, 2000, and 2004 editions of the Olympic Games. She won a gold medal in 1996 and 2004, and a silver medal in 2000. She missed the 2008 Summer Olympics due to the birth of her child.
Unlike several of her longtime teammates (among them Joy Fawcett, Julie Foudy, and Mia Hamm), she did not retire after the team's "farewell tour" which finished on December 8, 2004.
On January 18, 2006, Lilly made her 300th international appearance in a game against Norway. In the same match, she equaled Michelle Akers for second place on the team's all-time goal scoring list with 105. Lilly was named as a finalist for the 2006 FIFA Women's World Player of the Year. She finished second in the voting to Brazil's Marta.
After the birth of her daughter, Lilly returned to the national team in December 2008. Her last match for the national team, representing her record 352nd cap, was a World Cup qualifying loss to Mexico (1–2) on November 5, 2010, in which she played for six minutes as a substitute.
