Kourtney was riding in the backseat of the car, on the phone with her friend Sarah, when she and her driver stopped to pick up Khloe for the event.
"Kim and I just got into the biggest fight," Kourt told Sarah. "She just was going so crazy. She was sending me the meanest text messages. You would die. She's like, 'You're the biggest ungrateful bitch.' So I said, 'God, you're such a petty woman.' And she's like, 'Is that a joke? I had to intervene when your stylist pulled the nastiest clothes for you for your birthday party...'"
That's when Khloe got in the car. "Oh, we're still fighting!" she said sarcastically. "Oh, good!"
"Basically, I got into the biggest fight with Kourtney today because she's just such a bitch. Like, on another level," Kim explained. "So I called Kourtney, and Kourtney like screamed at me on the phone and was like, 'You think I like your style? You have the lamest style!'"
Over in the car, Kourtney continued to read Khloe the text messages she exchanged with Kim. "I said, 'You're going to school to become a lawyer to help the world, and these are the kinds of problems you have?' And she's like, 'You're really a miserable human being, and you keep not understanding the issue because you all of a sudden turn into such a humanitarian and talk about the world's issues, which you've not contributed one ounce to the world, so...'"
"You f--king fake humanitarian ho," Kim says, referring to her sister, to her shocked mom. "I actually do shit for the world. And you f--king fake it all day long and act like, 'Oh, there's people dying, Kim!' And what the f--k are you doing about it? So shut the f--k up."
"Keeping Up with the Kardashians" airs Sundays at 9 p.m. on E!