07/15/2010 at 12:00 AM EDT
There will be more social shake-ups at Seattle Grace on Grey's Anatomy
Australian actress Melissa George guest stars starting with Thursday's episode as Sadie, Meredith's friend from the past. "I show up at her doorstep," George tells PEOPLE. "Sadie gets a job at Seattle Grace due to her father, which is yet to be explored. She's taking a leadership role at the intern society, which is hysterically funny. I haven't stopped laughing for six weeks."
Apart from inciting jealousy in Meredith's current best friend Cristina Yang, Sadie's character, who is bisexual, will be full of surprises--including possible romances, says George, 32. "I don't know whether it's male or female. It could be either; it could be both. We're all dying to find out."
George, whose other TV credits include Alias
and HBO's In Treatment
, adds that her appearance on the show is not related to Brooke Smith's departure
. "I wasn't brought on to replace anybody. What happened with Brooke was done weeks before I started."
What's more, the recent Internet chatter about the casting upheaval hasn't fazed the actors on the show, says George, "It's such a family."
So, if she were asked to stay on as a series regular, would she consider it? "Of course," she says. "I'm having a great time." --Lisa Ingrassia