The actress, who may be in town to support her rumored beau, art dealer Vito Schnabel, 26, started her evening Wednesday at a private event at Alex Rodriguez's home. Arriving around 8 p.m., Moore, 50, was dressed in a short blueish-gray romper and funky black glasses. Sources tell PEOPLE that she seemed calm, friendly and relaxed.
"She didn't even have a drink in hand," a source added of Moore, who spent time in treatment earlier this year.
According to one guest, Moore spent much of her time at the party in close conversation with Stacy Keibler. "They seemed like good friends," the attendee said, adding that she also chatted with Owen Wilson and Martha Stewart.
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And as the evening progressed, Moore began to loosen up.
"Demi seemed to be dancing for the cameras," one party source said of the actress, who was surrounded by flashbulbs and was "acting flirty" with Lenny Kravitz. Another source at the party said Moore was drinking Red Bull, and: "Demi was wild and crazy and having the time of her life, in a world all of her own."
As for Schnabel, he was spotted at the party, though the two never posed for photos together. But according to an E! report, the two didn't hide their PDA, and were even making out during the party.
Perhaps they'll step out more publicly together on Thursday night when Schnabel is expected to throw his official party with Stavros Niarchos at the Wall/W Hotel.
Reporting by LINDA MARX