Berg was born in Whittier, California and raised in nearby Santa Fe Springs, graduating from Santa Fe High School in 1993. Berg and her twin sister enrolled at Fresno State and started for the school’s softball team. In her first season, she was named a National Fastpitch Coaches Association Third Team All-American. The Bulldogs made it to the WCWS and took their first game before dropping back-to-back shutout games against eventual champions the Arizona Wildcats and the Oklahoma State Cowgirls on May 27, 1994. Berg had two hits in the tournament.

Berg would also join the United States national team in 1994, participating in the 1994 ISF Women’s World Championship, where the US team won the gold medal. Berg redshirted at Fresno State in 1996, the year that she won her first Olympic gold at the 1996 Atlanta Olympics. In 1998, she won her second gold medal at the world championships. At the 1999 Pan American Games Berg performed well in the gold medal effort, batting .375 for the tournament with 15 hits. In the 2000 Summer Olympics Berg drove in the winning run in the 8th inning of the gold medal game.

In her second WCWS appearance, Berg and the Bulldogs were shutout in their first game but rebounded strongly by winning their next three including shutting out eventual champion Arizona Wildcats in the semifinals. Berg hit a double and scored the eventual winning run. In the second game of the doubleheader, Berg singled in her first two at-bats and scored each time to take the lead, however, Arizona tied the score immediately and went on to win 6–3 on May 25, 1997.

From 2000 to 2003 she participated at tournaments with the national team. She added gold medals at the 2002 World Championships and 2003 Pan American Games to her resume, batting .471 in the Pan-Americans. In the 2004 Athens Olympics she started eight of the nine games, batting .368, and held a perfect fielding average. In the gold medal game on August 23, Berg had a hit in the eventual win over Australia. In 2006 Berg won her fourth consecutive World Championship in Beijing. Berg’s four World Championship appearances is a record for the event.

In 2006, Berg was named to 25th Anniversary WCWS Team. In 2012, she along with her 2004 Team USA teammates were named to the Olympics Hall of Fame.

In 2007 Berg returned to her third Pan American Games, where she won another gold medal, and was chosen to carry the U.S. flag during the closing ceremonies. At the 2008 Summer Olympics, she captured a silver medal with the Team USA, the only time in Olympic history the United States did not win the gold medal. Berg did not play in the gold medal game but did hit .500 for the tournament highlighted by a diving catch to save Monica Abbott’s perfect game vs. the Netherlands on August 17. After the finals, Berg along with teammates retired from international competition.

Berg joined the staff at the Oregon State Beavers program in 2011. In 2012, she helped coach them to a regional appearance.

She was named Oregon State’s head coach on August 27, 2012.

Berg was an assistant coach at Fresno State from 2000–2003, as she continuing to participate with Team USA. She returned to her alma mater coaching staff for 2005 and 2006 seasons. Eventually she left her post to train with the national team. Berg was invited to be an assistant coach with Team USA in 2012, helping them win a World Cup.