Ms. Barton ended up signing on last minute, even after the show had started filming. While the actress was aware of “The Hills,” she didn’t spend any time with the cast before shooting the reboot. Ms. Barton does know the Jenner family from “back in the day,” as well as Stephanie and Frankie Delgado. She’s since made organic connections with the cast. “Audrina I’ve become really close with, and we hang out as friends,” she said. She also mentioned Ashley and Jason Wahler as new additions to her social circle.

But entering into the drama that once plagued the cast members was an adjustment for her. “It was just funny in the beginning because they do have a lot of drama and history that obviously I’m not privy to,” she said.

Ms. Barton was skeptical about members of the cast herself. “I think what’s really interesting is the people I was most afraid of going into this turned out to be the easiest people to deal with, so I found that to be really funny, and it’s an obvious life lesson,” she said. “The people that you like right away are not always your real friends.” In particular, she found that to be true of Jason and Heidi, who she says is “really chill” (a word she hates). “The people that you have the most trepidation about turn out to be the best,” she added.

The irony of Ms. Barton joining the reboot is not lost on her, considering “The O.C.” and her character Marissa Cooper inspired the reality show. “In the beginning, there was an expectation of me to still remain being Marissa Cooper in this ‘Laguna Beach’ California world, but it’s not feasible at the end of the day,” she said. “You are going to see me.”

Ms. Barton was a star of “The O.C.” for three of its four seasons, departing when her character was killed off.

At the time, there were conflicting stories surrounding her departure. She maintains that leaving was her choice. “I just had a lot in my career that I wanted to do and accomplish,” she said. “I felt like things were really heavily reliant upon me, and I was getting no time to do any of the other offers that were out there.”