MTV publicist Emily Yeomans confirms Cavallari will replace Conrad on the show. The season-five finale on May 31 marks Cavallari's "Hills" debut.
The 22-year-old aspiring actress caught the bouquet at the April 25 wedding of the series' duo, Heidi Montag and Spencer Pratt. The event was filmed by MTV.
Cavallari became a celebrity in 2004 when MTV tracked her high school love life and rivalry with Conrad on the reality show "Laguna Beach."