updated 06/27/2011 AT 2:00 PM ET
•originally published 06/27/2011 AT 2:50 PM ET
Coming out for the grand opening of F6ix nightclub in Harris’s California college town of San Diego, Hef’s ex showed up with high-school girlfriends and even her mom.
“She danced the night away with her crew,” an onlooker tells PEOPLE. “Crystal seemed to be in a really great mood and was very friendly with staff and patrons.”
Adds the source: “She didn’t drink too much but did have some Veuve champagne.”
Harris, who got on the microphone at one point to “say hello to the crowd,” says the observer, left shortly before the club closed down for the night.
“I’ve been spending time between L.A. and San Diego,” Harris recently told PEOPLE. But I’ll always be friends with Hef and go to the Mansion all of the time.”
Additional reporting by MARK GRAY