Katy Perry** is once again living a teenage dream with John Mayer**.

The recently divorced "Wide Awake" singer, 28, got super flirty with her on-again musician beau, 35, during a recent night out in Hollywood. Hitting up Saint Felix on Nov. 10 to celebrate the birthdays of Hello Giggles blogger Sophia Rossi and New Girl co-creator Liz Meriwether, the tight twosome looked "so affectionate," a source told Us Weekly.

"John had his hand on Katy's back a lot, and they were kissing and holding hands," the party-goer said, adding that it looked like the pair were "full-on dating."

Also at the bash were fellow A-listers Jon Hamm**, Mindy Kaling, Nicole Richie, Shannon Woodward, and Perry doppelganger Zooey Deschanel, who works with both birthday girls.

"Katy and Zooey were joking about how they look alike," the source noted.

Perry and Mayer, who reunited in September after a brief separation in August, have been photographed out and about often in recent weeks. At Perry's birthday party last month, "they were in their own world," a guest told Us. "She didn't even talk to her friends much. It was just her and John. She's obsessed with him. She said hello to people but then went right back to him."

She "believes she can change" Mayer, a source explained of Perry's infatuation with the Hollywood lothario, whose jilted exes include Taylor Swift, Jessica Simpson, Jennifer Aniston, and Jennifer Love-Hewitt. "She doesn't want to be just another one of his conquests."

This article originally appeared on Usmagazine.com: Katy Perry, John Mayer "So Affectionate" at Pal's Star-Studded Bash