Heidi Montag had harsh words for her former best friend during filming on WEtv's Marriage Boot Camp.

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In a scene with a Lauren Conrad stand-in, Montag was seen addressing her ongoing feud with her one-time co-star on the Hills, claiming it was the designer's insecurities, which drove them apart.

“I was the best friend you’ve ever had," Montag tells the woman, who has agreed to play the part of Conrad, in a sneak peek of the upcoming episode. "Lauren, I forgive you for being so insecure in your life and so frustrated for everything that you went through that you felt like you had to blame it on me because that was easier."

Heidi Montag & Spencer Pratt Feud Over Children In 'Marriage Boot Camp' Sneak Peek?

During filming on the Hills, Montag and her husband, Spencer Pratt, started a rumor, which claimed Conrad had starred in a sex tape with her former boyfriend, Jason Wahler. Although there was no truth to the rumor, Conrad took offense to what her former friend had done and kept her distance from her from then on out.

"I forgive you for trying to ruin my life. I forgive you for everything,” Montag continued in the sneak peek.

Then, during a confessional with Pratt, Montag explained, "I'm done with my former best friend and I just want to let it go."

To see more of Montag's apology to Conrad, tune into Marriage Boot Camp on Friday at 9 p.m. on WEtv.