08/26/2012 at 10:00 AM EDT
There's no slowing down for Katy Perry
One night after supporting musical pal Ferras during his performance on Thursday at Bootsy Bellows
in West Hollywood, the single
"Teenage Dream" singer lent a hand to another friend.
Perry planned a special birthday party on Friday night for her close pal Jon, who is Ronan Farrow's – the son of Woody Allen and Mia Farrow – best friend.
Renting out all of SHOREbar in Santa Monica, Calif., Perry was joined by approximately 40 guests, including Ronan, Hilary Duff
and husband Mike Comrie, Ferras and the venue's owner John Terzian.
"At the stroke of midnight, Katy brought out a birthday cake that had Jon's face on it, and she sung 'Happy Birthday'," a source tells PEOPLE. "She was in good spirits, laughing and seeming to enjoy the night."
Guests at the intimate fete sipped from the bar's signature punch bowls, while listening to tunes spun by DJ beeFOWL.
Perry stayed until around 2 a.m., but "wasn't being a party animal," the source adds. – Dahvi Shira