In the 2016 WNBA draft, Copper was drafted with the seventh overall pick by the Washington Mystics. After playing one season for the Mystics, she was traded to the Chicago Sky as part of a deal that sent Elena Delle Donne to the Mystics and Stefanie Dolson, Copper, and the 2nd overall pick in the 2017 WNBA draft to the Sky. For the next three seasons, she came off the bench for Chicago. In 2020, she was re-signed by the Sky. In the 2020 season, she played in a starting role, with increased playing time per game and averaging over 14 points per game halfway through the season.