She previously played for the Washington Spirit, Seattle Reign FC, and Angel City FC in the NWSL, Canberra United and Western Sydney Wanderers in the Australian W-League, Suwon UDC in Korea's WK League, and Apollon in Cyprus's First Division.

[1] Nielsen captained the Tar Heels during her senior season and finished her collegiate career with 13 goals and 7 assists playing as both a defender and forward.

[11] The following week, she played the full ninety minutes in the forward position in a friendly against recent FA WSL champion Arsenal L.F.C.

[14] After the conclusion of the W-League season, Nielsen signed with Suwon UDC in the WK League in South Korea.

[18] On December 16, 2021 Nielsen was selected by Angel City FC in the 2022 NWSL Expansion Draft and went on to make twenty appearances and sixteen starts in her first season with the club.

[22] She scored the equalizer goal in the club's 2-1 win against Southern California rivals San Diego Wave FC on June 17.

[23] Angel City finished in fifth place during the regular season and advanced to the playoffs for the first time[24] where they were eliminated by Seattle Reign FC in the quarter final match.

[25] On April 20, 2024, Angel City FC announced that Nielsen had been traded to the Houston Dash in exchange for $50,000 in allocation and $50,000 in transfer funds.