Born in Philadelphia to two healthcare professionals, Washington is a graduate of the Philadelphia High School for Girls. She earned her B.A. from Antioch University in Philadelphia in 1989. She then moved to Baltimore to attend Johns Hopkins University, where she earned an M.A. in 1992 and a PhD in 1997, both in sociology.
She began her professional career in academia, teaching at Lehigh University from 1995 to 2000 and working as a research fellow at the University of Pennsylvania from 2000 to 2001. Subsequently, she has worked for government agencies in Maryland, including the Maryland Secretary of State's office and the Baltimore Housing Authority, as well as nonprofit organizations. She is currently an associate director with the Parks & People Foundation in Baltimore.
Washington first ran for the House of Delegates in 2006, seeking one of three seats in Baltimore's 43rd district. She was one of six Democrats to run in the district. The field included all three incumbents: Curt Anderson (first elected 1982), Ann Marie Doory (first elected 1986) and Maggie McIntosh (first elected 1992).
Washington finished fourth in the Democratic primary held on September 12, 2006, behind the three incumbents.
Washington mounted a second bid for the House of Delegates in 2010, also in the 43rd district. This time, only two incumbents were seeking re-election: Ann Marie Doory had retired in July 2010 and her appointed successor, Scherod C. Barnes, was not running for a full term. Once again, six Democrats filed for three seats but Washington now had the support of the other incumbents – she joined the slate of Sen. Joan Carter Conway and Dels. Maggie McIntosh and Curt Anderson. All four of the slate's members won the primary, with Washington winning by a comfortable margin.
In the general election, the three Democratic nominees faced no opposition in a district that's overwhelmingly Democratic. They were elected unopposed.2014 Race for Maryland House of Delegates – 43rd District
Washington currently serves on the House Appropriations committee. In the 2013 session, she co-sponsored HB 860 (Baltimore City Public Schools Construction and Revitalization Act of 2013). Signed by the Governor on May 16, 2013, the new law approved 1.1 billion dollars to construct new schools in Baltimore City.
Washington is openly gay. She is one of six openly LGBT members of the Maryland General Assembly, alongside Sen. Rich Madaleno (D–Kensington) and Dels. Maggie McIntosh (D–Baltimore), Luke Clippinger (D–Baltimore), Anne Kaiser (D–Burtonsville) and Bonnie Cullison (D–Silver Spring). McIntosh is also a delegate from the 43rd district; Washington's election marked the first time in Maryland history that two openly LGBT legislators were elected from the same district. Washington is also one of only two African American lesbians to serve in a state legislature: the other is Simone Bell, a Democratic member of the Georgia House of Representatives.
A Presbyterian, she was an elder at First and Franklin Presbyterian Church in Baltimore from 2002 to 2005.