Heidi Montag Admits It's 'Frustrating' Adding Mischa Barton to 'The Hills'

Heidi Montag is not one of the many people excited to see Mischa Barton join the cast of The Hills: New Beginnings.

The reality television personality opened about not vibing with The O.C. star at first, saying she was not enamored by her aloof personality in the beginning.

"I think it was a little frustrating for me at first, because, like, we've put our whole lives into this show before and after, so to have someone come in and, like, be so reserved was a little bit frustrating," Montag admitted to Us Weekly earlier this month.

Montag added: "I don't think it was intentional, I think that is, like, how she is, and she's just a little more closed and needed a little more time to open [up]."

Co-star Jason Wahler also said he found Barton to be closed off when he first met her.

"She was very sheltered in the beginning. Very sheltered and shy and I think as I've gotten to know her... she was definitely...:

"...misunderstood," Wahler's wife, Ashley Wahler, added.

"I feel like she's, like, a little timid and not as, like, open as the rest of us, but then as soon as you hang out with her she becomes more real and raw," Ashley said.

Frankie Delgado said Barton also acknowledged she had a hard time welcoming the cameras into her life in the beginning.

"What we do is really hard to do and I think that she kind of proved it right," he said. "Like, she was like, 'Yo, listen, this is the hardest thing I've done.'"

He added: "You gotta put yourself out there... People can spot that fakeness."

Regardless of the bumpy start, the cast agrees she is a great fit on the MTV reboot.

"I think she's really quirky and funny and... she's a great addition to the cast. I really like Mischa," Montag told the publication.

Barton recently opened up to Entertainment Tonight about her role on the revival, sharing fans can expect to see more of her personal life than ever before.

"I mean, yes, there's some of that going on," she said of the series showing her dating experiences. "You'll have to watch to find out."

The show will also see Barton working on returning to acting. "You'll see on the show, I'm going on auditions," she added. "And I'm getting back out there and I've been doing that, developing stuff, I'm just not sure what it will be yet. But yeah, I'm definitely game for that."

The Hills: New Beginnings premieres Monday, June 24 at 9 p.m. ET on MTV.