People reports that on Jan. 11, Demi hit hot spot Beacher's Madhouse in Los Angeles with daughter Rumer Willis, 23.
Dressed in a miniskirt and quaffing Red Bull, Moore initially "kept to herself," relays an eyewitness. "But she started loosening up and getting into party mode. She seemed really happy to be out with her daughter's friends."
Moore also seemed really happy in the company of dark-haired TV actor Ryan Rottman, 27, who has appeared on "90210."
"She found ways to touch him all night, and at one point when he was in front of her, she was grinding on his butt," says the spy, who also recalls that Rottman's "shirt came unbuttoned, and she started tickling his bare chest playfully."
Us, meanwhile, has a slightly different take, quoting an onlooker as saying the "super skinny" star was "table dancing while three guys sat there watching. She was trashed."
This wasn't the first time in recent days that Demi got her dance on for an audience ...