Kristin Cavallari Attacks Stephanie Pratt

Kristin Cavallari Attacks Stephanie Pratt

On Tuesday's episode of The Hills, Kristin Cavallari rips into Stephanie Pratt for spreading rumors that she has been abusing cocaine.

"You love to run your mouth and make s--t up!" she tells Pratt, 24, who was arrested for a DUI last year and has battled drug problems.

Denying she spread any rumors, Pratt shoots back, "You have the bitchiest attitude! You can't even have a nice conversation ... You're just a mean person!"

Pratt demands an apology from Cavallari, 23, but she refuses to give her one.

"You're delusional," Pratt says as she storms off.