Actress Freema Agyeman has just landed a coveted role on the upcoming "Sex And The City" prequel one of the most coveted slots in Hollywood right now as she will star on the new CW series "The Carrie Diaries."   The prequel to the HBO series, Freema will play Larissa, a hip, cutting-edge editor/party girl who works at "Interview" magazine and who serves as Carrie Bradshaw's mentor when she arrives in NYC in the 1980s. AnnaSophia Robb, will take on the starring role of the young Carrie Bradshaw.