Whispers flared that life was imitating art after Jamie-Lynn Sigler, 27, guested on the HBO comedy as 28-year-old Jerry "Turtle" Ferrera's love interest.  Now the pair have shown the world that their entanglement is true.

The Sopranos Mafia princess and the Entourage hanger-on arrived (and stayed, according to an eyewitness) arm-in-arm for the duration of GQ's Men of the Year party at West Hollywood's Chateau Marmont Tuesday night.

Our spies say the pair were sweet but casual with one another.

"She was with a bunch of girls," the source says, "and he was off hanging with Kevin [Connolly], Lukas Haas and Leo [Dicaprio]. He would check back with her, go to the bar, check back with her and so on."

Nice to know the kids are taking it slow and steady. Jamie's got career aspirations after all.