Memo to Harry Styles** about Taylor Swift: If you wanna be her lover, you gotta get with her friends.

On Thursday, Dec. 6, the One Direction singer, 18, did exactly that when he met up with his country sweetheart, 22, at a birthday celebration for one of her gal pals in New York City. Among the guests at the shindig? Swift's longtime BFF Emma Stone.

The "Red" singer and the Gangster Squad actress, 24, had been enjoying a night out with friends at the McKittrick Hotel, where they hit up Manderley bar and then caught a production of the interactive theater experience Sleep No More. After the show, they moved the party to the Crosby Street Hotel, where they were joined by Swift's new beau.

A source tells Us Weekly that the superstar blonde was "all over" the boy-bander at dinner, even making out with him at the table in front of the other 10 or so guests.

Swift and Styles were first spotted together on Nov. 15 at an X Factor performance rehearsal in L.A., where onlookers revealed they saw the duo walking hand-in-hand. "They lit up when they saw each other," a source told Us of the new couple, adding that the "I Knew You Were Trouble" singer "was a puppy dog" around Styles.

Things must be going well if Swift is introducing him to her pals, who she has said are "like sisters" to her.

"My friends are amazing and I'm so thankful to have them, [but] the ones that are like sisters to me are Selena Gomez and Emma Stone," she revealed to PopSugar last year. "They can predict my thoughts; I've known them for so long it's really cool to have friends that are that close."

This article originally appeared on Usmagazine.com: Taylor Swift Makes Out With Harry Styles, Introduces Him to BFF Emma Stone