PDA alert: Taylor Swift and Harry Styles make out in Manhattan

By Kat Giantis

Taylor Swift's romance with Harry Styles is cruising along at warp speed. Seems they've already progressed from lovey-dovey photo ops and sleepovers to BFF introductions.

On Thursday night in New York, the confessional chart-topper, 22, introduced her One Direction beau, 18, to close pal Emma Stone as they helped celebrate a friend's birthday.

According to Us, Taylor and Emma rendezvoused with Styles at the Crosby Street Hotel bar following a night out on the town.

Swift must have missed the British boy-bander during those long, arduous hours apart, because she was "all over" him during the get-together with 10 or so friends, including starlet Dianna Agron.

Word is, they also weren't shy about demonstrating their make-out technique.

"Taylor and Harry [were] being very smoochie," a source relays to People. "They definitely [looked] like a couple."

The spy adds that as Harry held Taylor's hand, he appeared "very protective" and made sure to keep his arm firmly around her.

"They're not trying to hide it," the snitch says of their PDA. "The bar was packed."

Swift and Styles exited holding hands (photo at left), and reportedly headed back to her hotel.

Their public saliva-swapping caps off a well-documented week of together-time for Haylor, who hit the Central Park Zoo on Sunday, sang karaoke on Monday and reportedly enjoyed several sleepovers. Click on for highlights …