The beauty, who is five months pregnant with her first child, has already won a Golden Globe for the same role.
Hit US television show Lost was another early winner, with the cast taking home the Best Ensemble Performance Award For A Dramatic Television Series Award.
Kiefer Sutherland was named Best Actor In A Dramatic Series for his work as a US agent on TV show 24, while GREY'S ANATOMY star Sandra Oh won Best Actress In A Television Drama for her role as a doctor in the US series.
Oh dedicated her award to her fellow Asian American actors, saying, "I share this with you and be encouraged and keep shining."
Gay cowboy movie Brokeback Mountain is widely expected to dominate the awards after winning Best Picture at the 17th annual Producers Guild Of America (PGA) awards last week (22JAN06) and taking four top honours at the Golden Globes (16JAN06).