Katy Perry makes first appearance since Russell Brand split

Katy Perry may be newly single, but she doesn't exactly seem ready to mingle.

This weekend, the 27-year-old pop star seemed "subdued" as she made her first public U.S. appearance since splitting from hubby Russell Brand last month, an eyewitness told amNewYork.

While her friends danced and partied at Friday night’s event for GiveLove.org, a charity dedicated to improving the situation in Haiti, at Las Vegas' 1OAK, Perry "pretty much sat in the same spot the whole night," the insider said.

“She just sipped on one drink and seemed to be having a really mellow night,” the source said of Perry, who was sporting bright-blue locks and a bejeweled cocktail dress.

While she appeared to be in good spirits, Perry “was not at all in a party mood” and headed back to her room with her girlfriends relatively early, the source added.

Meanwhile, guests — including Paris Hilton — kept things going on the dance floor until 4 a.m.

Brand, 36, filed for divorce from Perry on Dec. 30, after about a year of marriage. Rumor has it that the comedian is already dating other women.