Khloe Kardashian is accusing Jordyn Woods of lying in a tell-all interview with Jada Pinkett Smith.
Woods went on Pinkett Smith's Facebook show Red Table Talk to discuss allegations she kissed Tristan Thompson, the father of Kardashian's child, at a house party.
It's not the first time Thompson has been accused of cheating, allegedly caught on camera with other women shortly before Kardashian was due to give birth.
But this latest apparent betrayal cuts deeper, as Woods is the best friend of Kardashian's younger sister Kylie Jenner.
Woods downplayed the incident, claiming Thompson merely kissed her without tongue, and she didn't know how to respond.
"On the way out, he did kiss me," she said, later adding there was "no passion, no nothing... he just kissed me."
She said she tried to apologise to Kardashian over the phone and offered to take a lie detector test to prove her side of the story.
"I did as much apologising as I could do, over the phone, over text."
But Kardashian has accused her of lying, claiming Woods is the sole reason she broke up with Thompson.
"Why are you lying @jordynwoods ?? If you're going to try and save yourself by going public, INSTEAD OF CALLING ME PRIVATELY TO APOLOGIZE FIRST, at least be HONEST about your story. BTW, You ARE the reason my family broke up," she said in a tweet.
She later tweeted to say Thompson was being held accountable too, but it was being done privately.
"Tristan is equally to blame but Tristan is the father of my child. Regardless of what he does to me I won't do that to my daughter. He has been addressing this situation PRIVATELY. If Tristan were to lie publicly about what conspired, then yes I would address him publicly as well."
Responses to the tweets were mixed. Some people blamed Woods for getting involved with Thompson, while others pointed out Kardashian, 34, was publically abusing a 21-year-old.
"Obviously once a cheater, always a cheater, and he's the one to blame, BUT Jordyn broke the trust of an entire family who built her," one person said.
"We are the same big age and I cannot even imagine treating my little sister's friends this way. Not to mention you are holding her to a standard you can't even claim for yourself. Do better," another wrote.