Tension in "The Hills"

The fourth season of The Hills kicked off to--what else? A great heap of drama!

Barely minutes into the season premiere, housemates Lauren Conrad, Lo Bosworth and Audrina Patridge fell into a heated catfight during a birthday party that L.C. and Lo "lovingly" threw for their dark-haired roomie.

"I feel that I don't click with you," Audrina told Lo. "We'll never be friends."  But though she's accused Lo of being "super-bitchy," is Audrina's problem merely a case of petty jealousy?

Insiders say Audrina is throwing a fit because she's no longer Lauren's number one sidekick on the show.  That spot has been filled by Lo – Lauren's BFF from Laguna Beach. Sources tell OK! the switch makes sense.

"Lo and LC have grown up together," a source close to the girls says.  "They have a history Audrina will never have."

As a result, Audrina, 23, has been chilly towards Lo, 21, and growing distant with Lauren, 22.  "Audrina got jealous and felt herself being pushed out," an LC insider says.  "She just gave up on the friendship."

Another friend of the trio confirms, "She Audrina was in this for the fame.  She always got along best with Heidi Montag.  She switched and became Lauren's best friend when they needed someone to move in with her."

For the latest Hills drama, pick up this week's OK! — on newsstands now!