"It was really fun at first, and now it's like a nightmare," the 32-year-old said at a jewelry event she hosted for MeMe London in America in Beverly Hills on Saturday.
"There's a big divide," she said of reuniting with the cast of The Hills: New Beginnings. "You know, the stakes are a lot higher. We've got couples who are married with kids. It's not kind of just like, 'Oh, you cheated at the bar.' This is way more life-changing kind of stuff. I'm scared for everyone. And for myself. It's going to be gnarly."
Along with Pratt, stars Justin Bobby Brescia, Brody Jenner and his wife Kaitlynn Carter, Audrina Patridge, Whitney Port, Spencer Pratt, Heidi Montag, Jason Wahler and Frankie Delgado — along with newcomers Mischa Barton, who starred on The O.C., and Brandon Lee, the son of Tommy Lee and Pamela Anderson — will also appear.
Brescia told Us Weekly that drama is "going to brew" between the cast members. "I think something's coming. I think a pregnancy might be coming," he said at the 2018 iHeartRadio Jingle Ball in Inglewood, California in November. "I can't tell you [who]."
Despite exes Brescia and Patridge spending quite a bit of time together during filming, he told Entertainment Tonight he has no plans of getting back together with his once flame. "You might [see me] meet a few ladies, but I'm so busy and fast. I'm too quick for love," he said.
"No, they're actually very sweet. You can't catch a villain this time," Brescia said. "We're a little devilish."
Delgado previously said that he wasn't sure how Barton would fit in with the rest of the cast, who was already "really tight."
"I know Brody use to be friends with [Mischa], but I only met her once, 10, 12 years ago maybe — back in the day when she was on The O.C.," he said. "It'll be interesting the way they bring her into our cast and into our friendships because we're all really tight with each other. But in the end, I think we have a really cool dynamic between all of us."
The Hills: New Beginnings is expected to debut in 2019.