While the show's still reeling from the loss of Katherine Heigl, “Grey’s Anatomy” has announced the addition of Mandy Moore as a guest star in the upcoming season finale.The two-hour Seattle Grace season ender will be airing on May 20, with Miss Moore to play the character of a patient named Mary.While it's know that Mandy's character will be treated by Chandra Wilson’s Bailey and her team, the rest of the details are being kept under wraps.Getting busier and busier as of late, Moore also recently signed on to star alongside "Twilight" actor Kellan Lutz in the Dermot Mulroney directed film, "Love, Wedding, Marriage."
