In a new preview for Keeping Up With the Kardashians, Kim tells her sisters, Kourtney and Khloe Kardashian, about how their younger brother, Rob, surprised her on the phone by having her talk to Chyna. Kim, 35, and Chyna, 28, used to be close friends -- with Chyna even attending Kim and her husband Kanye West's wedding in Italy in 2014 -- before Kim's younger sister, Kylie Jenner, started dating rapper Tyga. Tyga is Chyna's ex-fiance and the father of her 3-year-old son, King Cairo.
"So I called Rob, and he said Chyna wants to talk to me, so I just told him I'll talk to her when I'm ready," Kim recalls. "And he put me on speaker, and he's like, 'Oh, Kim, Chyna's in the room. I just wanted to tell you so you didn't think I was alone.'"
Kim says Chyna greeted Kim with a "Hi" in the background, but the reality superstar froze because she didn't know what to say. Things got even more awkward when Rob put Kim on the phone directly with Chyna while he was brushing his teeth.
"And so I say, 'OK, I gotta go, bye,' and hung up," Kim admits.
Later, in a solo interview, the mother-of-two acknowledges that Tyga dating 18-year-old Kylie "completely broke Chyna's heart." Kylie and Tyga ended up breaking up earlier this month.
"I completely feel for [Chyna] in that situation," Kim says. "Was it uncomfortable for me when Kylie and Tyga started to date? Absolutely. Because Chyna was my friend, but I had no choice but to take my sister's side -- that's my sister."
"I just wasn't ready, you know, and I'm not gonna be forced to be on the phone with her," she continues.
"My thing is, do what you want, do what makes you happy. But he should have said to us, 'Hey guys, this is how I feel, I can't help who I love," Kim stressed. "Kylie should know this. He just has no loyalty."
Rob and Chyna are now, of course, engaged and expecting their first child together. And it appears there's no longer any bad blood between Kim and Chyna. ET caught up with Kim in Cannes, France, on Tuesday during the Cannes Film Festival, where she said she was "really happy" for the couple.
"I mean, it's so exciting. It's a really exciting time for him," Kim told ET exclusively at the de Grisogono party. "I think he'll be the best dad. He's really just such a good, good person."