She previously played for the Philadelphia Independence in the WPS and represented the United States on the under-15, under-20, and under-23 national teams.

She was rated as the number two overall recruit in the nation by RISE Magazine and Soccer Buzz and was named Gatorade Player of the Year for the state of California.

In 2009, Barnes was one of just three players who started all 25 matches and ranked fourth on the team in scoring with 14 points (two goals and ten assists).

[8] They faced regular season winners Western New York Flash in the WPS Final where they were defeated 5–4 in penalty kicks after a 1–1 draw.

[11][12][13] Barnes was key component in the Reign's defense playing primarily as a center-back for the squad throughout the 2013 season.

During a home match against FC Kansas City on June 9, 2013, her defensive skill was especially highlighted when she reached a shot just before it crossed the goal line that had bounced over goalkeeper Hope Solo's head.

[14] Along with teammate Christine Nairn, Barnes was one of only two players on the Reign to play in all 22 matches during the 2013 season.

The team set a league record unbeaten streak of 16 games during the first part of the season.

[20] Following the regular season, Barnes along with goalkeeper Hope Solo and fellow defender Stephanie Cox were named to the Second XI team.

The Reign finished the regular season in first place clinching the NWSL Shield for the second consecutive time.

[25] Seattle was ultimately defeated 1–0 by FC Kansas City during the championship final in Portland.

[35] Following her successful guest stint, Barnes signed with Melbourne Victory the following season on a loan deal.

[37] In October 2017, she commenced pre-season training with Melbourne City, re-signing with them for the 2017–18 W-League season.

[42] In 2016, she received her first senior national team call-up for the 2016 SheBelieves Cup, but did not make an appearance.