Caught in the Act

Miley Cyrus Serenades a Drag Queen During a Girls' Night in Hollywood

07/10/2012 at 06:00 AM EDT

Bride-to-be Miley Cyrus had quite the night at Beacher's Madhouse at the Hollywood Roosevelt Hotel on Saturday night, leaving fiancé Liam Hemsworth at home while out with some gal pals and actor friend Ryan Rottman.

Cyrus, sporting a white sleeveless tee and denim shorts, arrived just after midnight, grabbed a front-row table and immediately started dancing to songs like Flo Rida's "Whistle" and Chris Brown's "Turn Up the Music." "She was in her usual happy mood and was very social and upbeat," an onlooker tells PEOPLE. "She was very chatty with everyone at her table."

After drag queen Vicky Vox toasted patrons' birthdays from the stage, she invited Cyrus to come up and sing her "Happy Birthday," since she was celebrating as well. Cyrus obliged, belting the tune a capella to the delight of the crowd.

The starlet stayed until the club closed down, sealing the night with a brief triple-kiss with her girlfriends.

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NEXT: Rachel Zoe and Baby Skyler's Mini Dance Party