The 35-year-old reality star revealed as much on the upcoming episode of Keeping Up with the Kardashians while discussing her half-sister's relationship with Tyga and the effect it had on the rapper's ex-fianceé, Blac Chyna.
"I understand that Kylie dating Tyga completely broke Chyna's heart," Kardashian said. "I feel for her in that situation. 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."
Kardashian commented on the situation after telling sisters Kourtney and Khloe Kardashian she recently avoided speaking to Blac Chyna on the phone. The star's brother, Rob Kardashian, who was dating Blac Chyna at the time, had tried to set up a conversation.
Jenner and Tyga split after the episode was filmed, while Blac Chyna and Rob are engaged and expecting their first child. Kardashian said she's "really happy" for the couple when she spoke to Entertainment Tonight this week.
"It's so exciting. It's a really exciting time for him ... It's just been a really fun time," she said at the De Grisogono party in Cannes. "I think he'll be the best dad. He's really just such a good, good person."
The new Keeping Up with the Kardashians episode will air Sunday at 9 p.m. ET on E!. Kardashian herself is parent to 2-year-old North and 6-month-old Saint and recently appeared on her first magazine cover since Saint's birth.