Teenagers can be intimidating. Doubly so if the teenager in question happens to be Billie Eilish, the biggest new pop star on the planet, with 32 million followers on Instagram, a fan in everyone from Justin Bieber to Melissa McCarthy, and Cool Teen swagger that could make any grown adult cower in insecurity. But then, Eilish, all lime green hair and baggy clothes, extends her arms out for a hug and for a second you think, maybe, just maybe "Am I cool?"

It was Saturday night in Shelter Island, and Sunset Beach was certainly the cool place to be. Chanel had all but taken over the Hamptons, shuttling an array of fashion, music, and actor types by private boat out to the beachside locale, where they were hosting a special dinner to celebrate the rebirth of the J12, the icon of CHANEL Watches. For the occasion, the house had transformed the restaurant and conjoining beachfront into the J12 Yacht Club, complete with Chanel-emblazoned sail boats, surfboards, and beach games. It was a hot night, even with the ocean breeze, and the Aperol Spritzes and glasses of frose were flowing, as guests like Kristine Froseth, Phoebe Tonkin, Maude Apatow, and Camila Morrone attempted to keep cool.

At this point, the musical guest was still under the pretense of a surprise, but a swarm of local teens stationed outside the restaurant all but gave it away to anyone who word hadn't trickled to by now: Eilish was due to give a rare acoustic performance around 9 p.m. It was 8:15 when the crowd swelled, as Eilish stepped out of her room at the adjoining hotel. Crowd aside, it was hard to miss the 17-year-old, who, despite the heat, was dressed in an oversized lime green t-shirt, baggy black pants, giant sunglasses, and lots and lots of jewelry—all Chanel.

"Oh girl," she said. "Obviously this jewelry—we got all the vintage stuff. We got these glasses. And look at my boot." This was no "Homeboy wore cowboy boots to the beach" moment; Eilish was in a boot boot, as in a medical encasing, following a recent ankle accident on tour. For the evening, it was swathed in fabric with the interlocking C pattern. "This is a Chanel scarf that I had people cut and sew for my sprained ankle," she said.

For all of Eilish's milestones over the past year, this trip served as a new check to the list: her first time in the Hamptons. "It's gorgeous," she said. "I mean, I've basically only been in my hotel, but yesterday we got on a boat and jumped in the water. It was fire."

Many things are "fire" to Eilish, but only certain things elicit a true, genuine excitement out of her. Meeting her idol, Avril Lavigne, which she happened to do just days before, is up there. "You haven't met her?" she exclaimed at mention of the meeting. "Girl. To think about how dope she is, number one, and how much she has been through—and now she is back. I also don't think she gets enough credit. And the whole conspiracy theory [that she was replaced with a double], I'm like, 'Shut up.' Dude, she suffered for many years and now is back on her feet and all anyone can be like is, 'That's not her.' Yeah it is, dude! She worked for the shit. She worked dude. There really are so many people that inspired me, but she really is on the very top of the list."

Of course, there can't be a mention of Eilish's idols without bringing the name Justin Bieber to the mix. A lifetime fan of the pop star, Eilish finally met him at this year's Coachella and last week, dropped a remix of her hit song "Bad Guy" with a new verse by the man himself. The cover art for the single was a throwback picture of Eilish in her childhood bedroom, which was covered in Bieber posters. Naturally, the internet took it upon itself to create an inverse of the image, with a young Bieber standing in front of Eilish posters. Rest assured, Eilish was thrilled with it. "It's unreal," she said, shaking her head. While doing so, her many Chanel jewels clanged together. And yes, it looked cool.