Ruffin-Pratt joined the Washington Mysticstraining camp roster in May 2013 after going undrafted in the 2013 WNBA Draft. In her rookie season, she played 34 games off the bench and averaged 4.4 ppg That year the Mystics made the playoffs finishing 3rd place in the Eastern Conference with a 17-17 record but were eliminated 2-1 in the first round by the Atlanta Dream. In her second season, Ruffin-Pratt continued her bench role with her playing time slightly increased. She averaged 4.5 ppg in 34 games and 6 starts. The Mystics were third place in the Eastern Conference yet again with a 16–18 record, but were eliminated in a 2-game sweep by the Indiana Fever. In the 2015 season, Ruffin-Pratt became the starting shooting guard for the Mystics. She played 32 games with 31 starts and averaged a career-high in scoring. Ruffin-Pratt scored a career-high 20 points in an 84-80 win against the Los Angeles Sparks on June 23, 2015. The Mystics made the playoffs finishing 4th place in the Eastern Conference with an 18-16 record and were a first round exit yet again as they were defeated 2-1 by the New York Liberty. In the 2016 season, Ruffin-Pratt moved to small forward in the Mystics starting lineup in order to make room for Tayler Hill at shooting guard. Ruffin-Pratt averaged 7.3 ppg in her new role at the wing, but the Mystics finished 13-21 and were eliminated from playoff contention. In 2017, Ruffin-Pratt re-signed with the Mystics once her rookie contract expired. During the 2017 season, Ruffin-Pratt started in all 34 games for the first time in her career. She briefly played the small forward role in the Mystics starting lineup during one of their starters' absence. After Hill tore her ACL, Ruffin-Pratt moved back to shooting guard. She averaged 7.3 ppg and the Mystics made the playoffs with an 18-16 record and the number 6 seed in the league following the league's new playoff format the previous season. The Mystics advanced all the way to the semi-finals after defeating the Dallas Wings and New York Liberty in the first and second round elimination games, marking the first time in franchise history the Mystics advanced past the second round. In the semi-finals, the Minnesota Lynx defeated the Mystics in a 3-game sweep. In 2018, Ruffin-Pratt was a role player for the Mystics, occasionally starting and coming off the bench. Her contributions helped the Mystics to a 22-12 record and the number 3 seed in the league. They received a bye to the second round. In the second round elimination game, they defeated the Los Angeles Sparks 96-64 to advance to the semi-finals for the second year in a row. In the semi-finals, the Mystics defeated the Atlanta Dream in five games to advance to the WNBA Finals for the first time in franchise history. In the Finals, the Seattle Storm swept the Mystics. In 2019, Ruffin-Pratt signed with the Los Angeles Sparks.
