Movieline says that the actress has landed a recurring role in the CW series.
Cobb will play Emily, the cousin of Annie (Shenae Grimes) and Dixon (Luke Wilson).
Emily is said to be a country girl who pretends to be more naive than she is. She reportedly wants to steal everything from Annie, including her boyfriend Liam (Matt Lanter).
Cobb has previously had roles in television shows including Jonas, The Mentalist, Medium and CSI: Miami.
She is expected to make her 90210 debut in January. The show continues on Mondays at 8/7c on The CW.