Is on-again, off-again couple Demi Lovato and Wilmer Valderrama officially back on again? It sure looks that way! How else to explain why the former X Factor judge — who just confirmed she’ll be leaving the show to focus on her music career — met up with Wilmer at the intimate Christmas dinner he threw for the staff of his production company, WV Enterprises, last night in L.A.?

We’re told that shortly after Wilmer and his co-workers arrived, Demi was seen pulling up to RivaBella restaurant in West Hollywood, where she discreetly joined the party. There, the group dined on house specialties including roasted bell peppers and burrata, octopus salad, and linguine with sea urchin sauce. Rocking blue hair, Demi seemed to be in a great mood, according to an onlooker — and Wilmer seemed happy to have her there.

They weren’t the only famous couple in the hot, new eatery. David Arquette and his pregnant girlfriend, Christina McLarty, dined at a nearby table.

Demi and Wilmer didn’t arrive together, but the burning question remains: Did they leave together? Not quite, says our tipster, who explains that Demi exited the dinner early, while Wilmer lingered to say good night to all his guests. But after giving everyone the slip, we wouldn't be surprised if they hooked up again later on!

Worth noting: Now that Demi’s quit X Factor, she’ll have plenty of time for other things…like spending time with old boyfriends. We’ll keep our eyes peeled!