Some casting shake-ups on Clint Eastwoodâs J. Edgar Hoover biopic J. Edgar today: Ed Westwick (Gossip Girl) officially joins the cast, while Charlize Theron opts not to take on the role of Hooverâs secretary. Westwick is set to play a clean cut operative who, after being assigned to write Hooverâs biography, begins to dig a little too deep into the enigmatic FBI directorâs life. A few days ago, we told you that Armie Hammer (The Social Network) had signed on to star as Hooverâs lover and confidant Clyde Tolson opposite Leonardo Dicaprio as Hoover himself. Damon Herriman (FXâs Justified) and Dame Judi Dench round out the cast announced thus far, with Dench portraying Hooverâs mother. Deadline reports that Eastwood is now looking to cast either Amy Adams or Naomi Watts in the role of Hooverâs secretary.Vulture reports that Theron, who was never officially attached to the film, has ultimately decided not to take part in the film. Instead, the actress has signed on to star in Rupert Sandersâ Snow White and the Huntsman, and may be mulling over Ridley Scottâs Alien prequel. More after the jump.In addition to reporting Westwickâs addition to the cast of J. Edgar, Deadline also says Theron has officially signed on for Snow White and the Huntsman. Back in October, we told you that she was eying the role of the evil queen in the film Now it appears sheâs decided to star in the film after-all. With little movement on the flick as of late (other than more casting rumors), this could mean that production is gearing to start up soon.Now on to that Alien rumor: While thereâs no official word on this, and casting rumors regarding the Alien prequel have run rampant the past few months (not to mention highly inaccurately), Vulture is reporting that Theron will âget the new version of the Alien script sometime this week and make her decision soon.â They claim that Fox execs are keen on grabbing a big name star for the project, while Scott is partial towards Noomi Rapace (The Girl with the Dragon Tattoo). Apparently, if Scott casts Rapace as the star, the studio wants a big name actress to take on the supporting role of "Vickers." This supporting role is apparently being expanded, and that's the role that Theron is looking towards when she reads the script. Take this with a grain of salt, as thereâs been little official news on the project as of late other than the denial of all previous casting rumors/supposed plot details.Theron is currently filming director Jason Reitmanâs Young Adult, from a script by Diablo Cody (Juno). The film stars Patrick Wilson and Patton Oswalt and is set to be released sometime this year.