At 16, Brittany's first big acting job was on the teen drama Swans Crossing (with Sarah Michelle Gellar), before she joined her sister on Sweet Valley High. The popularity of the show earned both sisters a Young Artist Award in 1995 for playing the Wakefields. After Brittany graduated from Sweet Valley, the Florida native's next role of significance was in 1999, playing Eve Whitman, Jen Lindley's (Michelle Williams) half-sister, who was mysteriously attracted to Dawson, for 4 episodes in Season 3 of Dawson's Creek.

She starred in That 80's Show, Joe Dirt, Joe Dirt 2, White Chicks, It's Always Sunny in Philadelphia, and BET's The Game, where she began as a recurring character (Kelly Pitts) in Season 7, and was upped to series regular in Season 8. In 2007, Brittney won Best Actress at the New York International Independent Film and Video Awards for her role in Last of the Romantics. Her most recent role, as of 2016, is on ABC's Black-ish.