The singer was spotted last night after the surfboard show having a B-day dinner with boyfriend Justin Bieber and small group of friends and family at Beverly Hills restaurant Il Cielo.
The two arrived on the "Boyfriend" hitmaker's customized Mercedes minibus.
Hosted by Gomez's mom, Mandy, the dinner for 12 took place in the private back patio with the floor covered in rose petals to match the singer's pink Dsquared2 minidress.
The get-together started with cocktails (ginger ale for Gomez and Coca-Cola for Bieber!) followed by dinner and a flourless chocolate birthday cake topped with fresh raspberries and whipped cream.
"Selena was just a doll, so humble and sweet," restaurant owner Pattie Vericella tells E! News.
Last night's fete was nothing compared to the partying Gomez has been doing with older pals Vanessa Hudgens, 23, and Ashley Benson, 22.
"Vanessa and I are all drunk and coked out in the movie," Benson (looking fab in Balenciaga and Monique Lhuillier) told me on the pink carpet at the Teen Choice Awards. "Selena is just drunk, not coked out."
Don't worry that Selena's gone over the edge. The trio play party-hearty coeds in the upcoming indie flick Spring Breakers. And they used crushed vitamin B12 for the lines of cocaine they snorted in the movie.
Playing liquored up proved to be a lot of fun.
"It's awesome," the Pretty Little Liars beauty said. "We sing a lot of Britney Spears when we're drinking in the movie. We do a lot of crazy stuff."
—Additional reporting by Brandi Chang
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