Cavallari was in attendance at Heidi Montag and Spencer Pratt's weekend wedding, according to E! News, which added the nuptials broadcast during The Hills May 31 episode will "kick off" Cavallari's arrival on th show.
The May 31 episode will also be Conrad's last after she announced in February that the show's currently-airing fifth season would be her last season on the show. Conrad had reportedly already completed her fifth-season filming several weeks ago before changing her mind and deciding to attend Montag and Pratt's wedding ceremony after all, according to E! News.
Both Cavallari and a The Hills rep could not confirm her participation in fifth-season episodes scheduled to air this fall, however MTV has previously stated Audrina Patridge, Brody Jenner, Stephanie Pratt, Lauren "Lo" Bosworth, Justin Bobby, and several "fresh faces" will appear.
Cavallari and Conrad first met as students at Laguna Beach High School -- where Cavallari was a junior and Conrad a senior -- and both appeared on Laguna Beach when the MTV reality series premiered in Fall 2004. However they were weren't close friends, as Cavallari was dating Conrad's long-time childhood friend Stephen Colletti.
Cavallari and Colletti's relationship eventually fizzled. Ironically, Cavallari then dated Jenner until 2006, which is when Conrad began a coy romantic relationship with him.
While Conrad moved to Los Angeles and appeared in Laguna's The Hills spinoff, Cavallari started acting in the scripted genre with cameos in Veronica Mars and Cane as well as roles in such films as Fingerprints and Spring Breakdown.
She also served as co-host for the UPN reality series Get This Party Started, where she worked with professional party planners to throw bashes for deserving people at significant points in their lives. The show premiered in January 2006 and was subsequently canceled after airing only two episodes.