AceShowbiz -

Kylie Jenner stepped out with her sister Kourtney Kardashian's ex-boyfriend Scott Disick following her split from Tyga. Kylie and Scott attended the Nylon and BCBGeneration's Annual Young Hollywood May Issue Party at Hyde Sunset on Thursday night, May 12.

Kylie donned a white jumper paired with leather skinny pants and pointy ankle boots. The "Keeping Up with the Kardashians" star styled her black hair in loose curls. At one point, she leaned her head on Scott's shoulder while posing for pictures.

Rumor has it, Kylie broke up with Tyga because of tension over his cheating allegations and the engagement of Rob Kardashian and Blac Chyna. A source told PEOPLE that the pair "were fighting a ton over stupid, petty bulls**t" over the last few months, and "she was over it."

Kylie, who "feels insecure about their relationship," decided to end it following Rob and Blac's engagement. "[Tyga] was lying repeatedly to her face and she just couldn't take it anymore," said the source. "She couldn't trust a word he said."

Back in November, the former couple briefly split because of trust issues as well. "She's caught him lying and talking to other girls behind her back before, and this was the last straw," another source said, "She feels super betrayed and is just so pissed off, damaged and hurt about it."