Kylie Jenner is "very torn" on how to handle the situation with Tristan Thompson

A source said: "The whole family is writing Jordyn off. [Kylie's been] in denial for days. She is very torn on how to handle the situation. Khloe is more disappointed that someone so close to their family would betray her. She can't believe it."

Khloe - who has had to deal with the pain of being cheated on before after Tristan was seen getting close to another woman just days before she gave birth to their daughter True 10 months ago - is "shocked" by Jordyn's betrayal.

An insider added: "She heard it from multiple people and doesn't believe him for a second. She is angry more than she is sad. And she's shocked Jordyn would do this. Of all the guys in the world, she can't fathom why Jordyn would make a decision like this. Khloe is reliving the worst kind of betrayal and pain all over again."

Tristan and Jordyn apparently got close when they went with a "group with mutual friends" to see Drake and went back to Tristan's for an after party.

The source shared to E! News: "Tristan and Jordyn were definitely hanging close to one another and were being very flirty. Tristan had his arms around her at one point. Jordyn stood by him the entire time they were out and he was laughing and smiling at her. Jordyn stayed at Tristan's house partying with him and his friends until the early hours of the morning, and they were very touchy. They sat together on the couch and were talking and cuddling for hours. They had chemistry the entire night and everyone could see it ... You could tell they were into each other."