The reality star was asked about the show on Watch What Happens Live and joked that she didn't mind saying it was largely constructed.
Asked if she was told what to say by producers, Cavallari replied: "Pretty much. Fake relationships, fake fights - yeah! Sorry!"
She also confessed that her relationship with her co-star Justin Bobby was made up, saying: "I never really dated him... I think I made out with him once, and that took a lot of convincing. And finally I was like, 'Alright, fine, I'll just do it'."
Cavallari admitted that her feud with Lauren Conrad had some basis in reality, but she added: "I feel like they put things in our heads. We were 17 and 18 and they made it a lot worse than it was."
However, Cavallari explained that she did not mind faking the show too much, saying: "It was fun, because you're acting. It was more fun for me."
Earlier this year, Cavallari welcomed her first son Camden Jack and has since said that she would like to have more children.
Watch Kristin Cavallari speaking about The Hills below (US only):