Styles is the Terps' fourth new addition of the offseason.
The Big Ten hasn't given official word about when the season will start.
All six former Terps in the WNBA made the playoffs.
Six former Terps are currently active and playing in the WNBA's bubble.
Charles, once expected to be a first round pick, slid to deep in the second last Friday.
Charles will go down as one of the all-time greats for Maryland women's basketball.
During her four years in College Park, Charles was a three-time all-Big Ten first team selection.