No more Mrs. Nice Guy. Kim Kardashian has long been the peacemaker between Caitlyn Jenner and the rest of the family. But even she has her breaking point — and it comes courtesy of the Olympian's tell-all.

In a clip from the Sunday, Oct. 1, episode of Keeping Up With the Kardashians, we see Kim reading a passage from the transgender advocate's memoir, The Secrets of My Life, that pertains to her late father Robert Kardashian Sr. She recites to sisters Kourtney Kardashian and Khloé Kardashian, “Robert Kardashian knew O.J. Simpson was guilty but joined the defense team to get back at his remarried ex. Robert told Caitlyn in secret, after the O.J. trial that he believed his friend was guilty.”

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This pronouncement comes after years of the Kardashian family claiming Robert believed O.J. to be innocent while he was defending the former NFL star in his murder trial. So reading this conflicting account from Caitlyn has the sisters shocked. Kourtney says in disbelief, “To sell a book, you’re going to make something up?”

For Kim, this betrayal is even more personal, as she notes that her former stepparent had assured her there was nothing to worry about. “It is so shady that Caitlyn came over and gave me the book and said, ‘Well, the final version has a few more things in it but don’t worry, it’s nothing about you,'” the mother-of-two admits to the camera. “So she lied to me, because it is about me if it’s about our dad.”

The confessional demonstrates a turning point in the KKW Beauty mogul’s approach to the 67-year-old going forward. “I have always had Caitlyn’s back, but she is a liar, she is not a good person,” she states. “My relationship with Caitlyn was strained and I just was trying to just be respectful. [But] if you talk about my dad, I will cut you.”

Seems like Caitlyn has also alienated herself from daughter Kylie Jenner, after she reportedly expressed how “disappointed” she was in the 20-year-old for getting pregnant with boyfriend Travis Scott. “She thinks Kylie is way too young to have a baby, and that she should have waited until she was in a long-term committed relationship,” the insider said.