In 2011, Caldwell was named to the preseason roster of
Women's Professional Soccer (WPS) franchise
magicJack but did not sign for the team. Instead, Caldwell played for Albany Alleycats in the
Women's Premier Soccer League (WPSL) in 2011 before joining Icelandic
Úrvalsdeild team
Þór/KA to finish the 2011 campaign. She scored two goals in eight appearances in all competitions including in a
Champions League round of 32 match against
Turbine Potsdam.
Avaldsnes Ahead of the 2012 season, Caldwell moved to
Avaldsnes IL of the Norwegian
1. divisjon. She played in 20 of 22 league games as Avaldsnes finished top and won promotion to the
Toppserien. In the following three seasons, Avaldsnes retained their Toppserien status with 4th, 5th and 2nd-place finishes with the latter qualifying the team for the
UEFA Women's Champions League for the first time, and also reached two
Norwegian Women's Cup finals: losing both the 2013 final 1–0 to
Stabæk and 3–2 to
LSK Kvinner in 2015. With the owner heavily investing in the club including bringing in national team players from Norway, Sweden, Iceland and Brazil, Caldwell faced heavy competition for her place in the squad during the 2015 season. Under the new management of
Tom Nordlie, Caldwell was limited to four appearances in 2015 and decided to leave at the end of the season: "At that time, a new coach had come in. I was working really hard to try to prove him wrong, but he obviously didn't fancy me as a player, didn't give me a chance." In total she played 66 games for Avaldsnes and scored eight goals.
1. FC Köln In January 2016, Caldwell joined
2015–16 Frauen-Bundesliga strugglers
1. FC Köln on a short-term deal as the club looked to bolster in a bid to stave off relegation. However, Caldwell played in six matches, all defeats, as Köln dropped out of the league.
SC Sand She left at the end of the season, opting to remain in the Bundesliga with
SC Sand following a successful trial with the club. She cited her spell at SC Sand, particularly under
Colin Bell who signed her for Sand and would later manage the Irish national team, as a rejuvenating experience following tough periods with Avaldsnes and Köln. Bell most notably took Caldwell from being a versatile utility player in midfield and at full-back, and told her to focus playing at centre-back. In August 2020, Caldwell was named captain in place of the departing
Anne van Bonn ahead of the
2020–21 season. Caldwell left SC Sand midway through the season to pursue another playing opportunity.
North Carolina Courage On 19 January 2021, Caldwell returned to the United States to join
North Carolina Courage of the
National Women's Soccer League, signing a one-year contract with an additional option year. In December 2021, North Carolina declined Caldwell's contract option at the end of the season. She had made eight appearances for the club.
Manchester United On 27 January 2022, Caldwell signed a short-term contract with
Women's Super League club
Manchester United for the remainder of the
2021–22 season. She made six appearances in all competitions before leaving the club at the end of her contract on 30 June 2022.
Reading On 11 August 2022, Caldwell signed with
Reading of the English
Women's Super League. ==International career==