Vegasis betting big on family drama.The O.C.and Nikitastar Melinda Clarke to play the mother of Sarah Jones' Mia Rizzo, TVGuide.com has learned exclusively. Clarke will play Lena, a charismatic, shrewd, strong woman who is attracted to even stronger men. Although Mia's father (Michael Wiseman) insisted that Lena died when Mia was a baby, she's alive and well, having been forbidden to see or contact her daughter. Naturally, her arrival at the Savoy will ruffle a few feathers.Speaking of ruffled feathers, as we first reported, Lena catches the eye — and a whole lot more! — of Vincent Savino (Michael Chiklis) before he learns her true identity. CSI. She's also appeared on such shows as Entourage, The Vampire Diaries and Chuck.Vegas airs Tuesdays at 10/9c on CBS. An airdate for Clarke's episode has not been set.