A source told Radar Online that "Kourtney and French were on each other" at the party at Isabel in West Hollywood. "She was twerking on him, he had his hand on her waist and a— and was whispering in her ear all night," the source said.
The two were reportedly "all over each other" and Kardashian "was eating it up," according to the insider. "She was smiling in his face and was hand feeing him hors d'oeuvres." The source continued, saying that Kardashian, 39, and Montana, 33, appeared "too close for comfort" and were "looking like they wanted to do some X-rated things."
Khloé, 34, and the rapper dated on and off in 2013 and 2014 after Khloe filed for divorce from NBA player husband Lamar Odom. After Khloé and Montana called it quits for the second time in December 2014, she said she wasn't ready for another relationship after her failed marriage to Odom.
“I jumped into something because I was just, like, lonely and destructive,” she said during an episode of Kourtney & Khloe Take the Hamptons. “But now I’m like, I just want to be alone." Her on-off relationship with Montana was going on before her divorce was finalized and before Odom's near-fatal overdose in 2015.
Kardashian's night out with Montana over the weekend comes a few months after she split from boyfriend Younes Bendjima and the same day that she was seen grabbing dinner with her ex Scott Disick and his current girlfriend, Sofia Richie. The three were spotted at Nobu in Malibu, California, with Kardashian departing the restaurant in a different car.
After the dinner, a source told PEOPLE that Kardashian "doesn't necessarily care to get to know Sofia better, but she feels she needs to because of the kids."
“Sofia spends time with Kourtney’s kids, so Kourtney wants to make sure they are all on the same page,” they added “Scott and Sofia tend to get into arguments. Kourtney wants to make sure the kids are in a positive environment when they are at Scott’s house. She is setting up rules for how things needs to be when the kids are with Scott.”
Another source said the dinner itself was "quick" and "seemed a bit tense."
"It wasn't like they are all friends and were hanging out for fun. It looked more like a business dinner," the source said.
Khloé admitted on Twitter that watching the drama unfold all over again was particularly difficult. “You may forgive but forgetting is not possible. Looking back that I was in shock because I couldn’t believe that this would ever happen to me but I’m still very proud of myself for how I handled everything. True gave me the peace and strength I needed,” she tweeted while the episode aired, referencing her and Thompson's six-month-old daughter.
“I chose to put my feelings aside for the birth and to try and have as much positive energy that I could. My only thought was about the birth of my daughter. I wasn’t going to let ANYONE disrupt anything less than what she deserved. Joyous love,” she added.