Lauren Conrad and Heidi Montag's Feud Heats Up

The Hills are alive with the sound of ... screaming.

Insiders claim in Us Weekly's current issue that Heidi Montag is so eager for more face time on the hit MTV reality series that she’s been crashing scenes with former BFF, Lauren Conrad.

“Heidi’s been showing up at shoots uninvited,” a source tells Us. “She knows her best chance for airtime next season [which premieres in August] is to be in sequences with Lauren.”

The drama came to a head May 30 after Montag, 20 – now engaged to Spencer Pratt, 23 – clashed with Conrad, 21, at L.A. nightclub Les Deux.

“Lauren was screaming, 'You’re pathetic!’” says a witness. “Lauren was using her hands wildly, saying she didn’t want to deal with Heidi.”

But Montag’s rep tells Us, “Heidi’s recording her album. She doesn’t have time to chase Lauren.”