Izzie is back — but her return could be short-lived.

After taking a three-month maternity leave to bond with her 15-month-old daughter Naleigh, whom she adopted in September with husband Josh Kelley, Katherine Heigl is due to return to the set of Grey’s Anatomy on March 1. Two weeks later, the actress, 31, will travel to Las Vegas to accept the ShoWest award for Female Star of the Year, a film-industry honor previously won by the likes of Angelina Jolie and Jennifer Aniston.

Is the award yet another sign that Heigl — who took a five-episode hiatus from Grey’s earlier this season to film the romantic comedy Life As We Know It with Josh Duhamel — is ready to depart Grey’s to focus full-time on her film career?

“It wouldn’t be a shock,” says a source close to the show. By the time Grey’s airs the finale of season 6 in May, Heigl will have been absent from roughly half of its 24-episode run.

Since joining ABC’s hit medical series in 2005, the actress hasn’t shied away from expressing her occasional displeasure with the show. She won a supporting actress Emmy in 2007 but announced the following year she was withdrawing her name from Emmy contention because she “did not feel that I was given the material this season to warrant an Emmy nomination.” Last July, the actress complained to David Letterman about returning to the Grey’s set: “Our first day back was Wednesday and it was — I m going to keep saying this because I hope it embarrasses them — a 17-hour day, which I think is cruel and mean.”

Then is the actress, who has five movies in development and an action comedy, Killers, due in theaters in June, indeed winding down her stint as Dr. Isobel Stevens? “The level of speculation is no different than it has been in the past couple of years,” says another show insider, who adds that casting changes are typical of a show with a six-season run.

Whatever happens, don’t expect an announcement before June, when the show’s cast typically learns about their contracts for the coming season. Heigl’s rep did not return calls for comment, and ABC declined to discuss specifics of their actors’ contracts. –Lisa Ingrassia

Tell us: What would you miss about Isobel Stevens if she left Grey’s Anatomy?Randy Holmes/ABC