Kristen Cavallari has just started filming scenes as Lauren Conrad’s replacement on “The Hills,” and it appears the newcomer is already creating drama.

Cavallari, who first became known as the bad girl on 2004′s “Laguna Beach,” made a bad first impression when she recently tried to steal the spotlight at Audrina Patridge’s 24th birthday party at L.A.’s London West Hollywood hotel, Starmagazine.com reports.

“Kristin was always making sure to yell out one-liners and hog camera time,” says an eyewitness.

When Cavallari began flirting with Patridge’s on-and-off boyfriend, Justin “Bobby” Brescia, the birthday girl reportedly lost it.

“Kristin was fake giggling and making it look like she liked him,” says a source. “Audrina started yelling at Kristin about how desperate she is and was clapping and yelling, ‘Keep it up! You’re such a good actress!’”

Adds the source, “Obviously, it’s not material they can use on the show, but Audrina didn’t care. She wanted to finally tell Kristin what she thought of her.”

But Patridge is not the only cast member fuming at Cavallari.

Heidi and Spencer Pratt are also angry about the new addition to the reality show, claiming Cavallari is stealing their spotlight.

“They feel like they worked their butts off for the show, and now Kristin just walks on and becomes the new star,” says a source.

It looks as though there was no worry with Conrad leaving “The Hills”, but Kristin Cavallari’s addition might put an end to it all.

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