Samantha Ronson (left) and Lindsay Lohan
05/29/2008 AT 01:15 PM EDT
and deejay Samantha Ronson's relationship appears to be a family affair.
The duo – who are "together," a source says in the new issue of PEOPLE – were spotted Wednesday afternoon lunching with Ronson's writer-mom, Ann Dexter-Jones and Lohan's sister Ali, 14, at the Italian restaurant Gino on Manhattan's Upper East Side.
Although Lindsay, 21, ate little of her veal parmesan, says a source, Dexter-Jones insisted the group indulge in dessert: "Cheesecake – with four forks!" she cheerily told the waiter, though Ronson, 30, opted for lemon sorbet.
Throughout the meal, the group engaged in a spirited session of girl talk, the source adds. And when the foursome left Gino's the wait staff collectively chanted, "Ciao, bella!, Ciao bella!"
While Lohan matriarch Dina, who's currently starring in E!'s Living Lohan
with Ali, wasn't spotted, she told PEOPLE, "I'm friends with [Samantha's] mom. She's raised some extremely talented kids. It's a talented family." Dina has also offered Samantha praise, telling PEOPLE she's a "sweetheart" and "true friend" to Lindsay.
Later that evening, Ronson spun at a Men.Style Women of Fashion party on the rooftop of the Peninsula Hotel, while her avid sidekick Lohan
remained in the hotel's lobby.
Meanwhile, a source tells PEOPLE that Lohan is due back in L.A. this week to start filming a movie.
Reporting by LESLEY MESSER, KRISTEN MASCIA and DAVID CAPLAN