"Most elegant princess in the world," Bieber wrote next to the split screen pictures of Gomez, which he shared with his 50 million Twitter followers.
The "Come and Get It" beauty, 21, looking all-grown-up and glam in the shots, wore a gold beaded halter neck gown with a sheer skirt from Emilio Pucci's fall 2014 collection for the hot party. She left her long brunette locks down and parted to the side, accentuating her expressive eyes with dark winged eyeliner.
Inside the star-studded bash, Gomez mingled mostly with pals Zooey Deschanel and Vanessa Hudgens, posting several Instagram pics from inside the after-party. Hugging her Spring Breakers costar Hudgens on a couch in one cute candid, Gomez wrote, "My only, official party buddy for life ;)."
As confirmed by Us Weekly, the pop star secretly went to rehab in January. "Selena voluntarily spent time at Meadows [in Wickenzberg, Ariz.] but not for substance abuse," her rep shared. The singer, meanwhile, addressed her secret rehab stay on Instagram on Feb. 10 and thanked fans. "I've done everything I could to the best of my ability," she wrote. "Thank you for the unconditional love and cyber hugs. You inspire me."
Her former flame, who turned 20 on Saturday, Mar. 1, posted a selfie of himself Monday morning with tussled hair. Resting his head against a pillow, Bieber wrote, "Good morning, god loves you."
An insider told Us that Gomez's close friends have been trying to keep the star away from Bieber. "Demi Lovato set up Selena and Niall [Horan]," the source revealed after a sighting of Gomez and the One Direction heartthrob was posted by a fan in mid-February.
Gomez, who covers the March 2014 issue of Seventeen magazine, recently discussed her first love and recovering from heartbreak: "This year is when I really started feeling powerful," she said in the interview. "I actually talked to Katy Perry about guys who are intimidated by strong girls. I haven't found someone yet who could understand my lifestyle, support it, love me through it, and not be threatened by it."