The pop star rushed to her party at a private home in Beverly Hills after performing at the NBA All-Star Game in Los Angeles. When she arrived, a party guest tells PEOPLE that she was treated to a taste of home – in the form of Sprinkles red velvet cupcakes with the Barbados flag imprinted on them, which she grabbed, announcing, "I'm so hungry."
Before all her guests had arrived, Rihanna managed to sneak away with her best girlfriends in a secluded room. When she joined the main party, she sported a tight-fitting pink dress with some purple fringe around the skirt.
"She [gave] Ryan Phillippe and Zac Efron huge hugs," the source says, adding that the two actors hung out together and chatted throughout the night.
Cee Lo Green and his crew were spotted too, noshing on some oxtail and plantains. Mary J. Blige and Jay-Z, who were "laughing and having a blast," posed for photos in a corner, the source adds. Blige also "squealed with excitement" when she caught sight of Diddy, and then hugged him.
Snoop Dog and Warren G rolled in at 1 a.m. and proceeded to dance and sing along to some old-school hip-hop songs while guests cheered them on.
Joel Madden and Christina Milian were also celebrating with the birthday gal, and indulged in vanilla and red velvet cupcakes.