"Without Lauren, like, she was always the one -- she's the leader, the one that would tell you what to do, what not to do," Patridge said.
"So now it's kinda like we all get... you kinda get to make your own choices and be your own self," she added.
Montag and Conrad clashed during "The Hills'" original run on MTV.
Montag recalled Conrad's famous "I want to forgive you, and I want to forget you" line in an interview with Entertainment Tonight published Monday.
FOLLOW REALITY TV WORLD ON THE ALL-NEW GOOGLE NEWS!
Reality TV World is now available on the all-new Google News app and website. Click here to visit our Google News page, and then click FOLLOW to add us as a news source!
"It was really a backstabbing moment for me. Like, 'We don't have the friendship that I thought, and I guess it is better for us to both kind of move on because I don't really need a friend like that either,'" she said.
Montag said she kept in touch with Conrad "off and on for a while" after "The Hills" ended in 2010 but hasn't spoken to the star recently.
She and husband Spencer Pratt teased renewed drama with their co-stars in the reboot.
"It's a volcano," Montag said.
"Oh my god, these are people that I have been avoiding these conversations [with] for 10 years," Pratt added. "It's like, 'Oh, I didn't forget. I have a notebook.'"
"The Hills: New Beginnings" will premiere on MTV on June 24 and features returning stars Montag, Pratt, Patridge, Stephanie Pratt, Whitney Port, Jason Wahler and Frankie Delgado.
Copyright 2019 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.