Scott's New Girlfriend! Disick's Sexy Model Exposed—Find Out Why He's Hiding Her From Kourtney

"They met during one of Scott's Las Vegas appearances a few weeks ago, and they've been partying together ever since," reveals an insider. "She's already inserted herself into Scott's life in a big way."

In addition to all-night ragers in Sin City, the Utah native has been traveling with Scott, 32, to out-of-town gigs on his private jet and keeping him company in his Beverly Hills bachelor pad.

"She absolutely loves living his lavish lifestyle," dishes the insider. "She's been bragging to all her friends about sleeping with him."

However, the father of three doesn't appear to share her enthusiasm. The blonde beauty recently tweeted a photo of the two cozied up poolside but mysteriously deleted it from her social media shortly thereafter.

"He doesn't want Kourtney to find out he's seeing someone," explains the insider, who claims Scott is pretty "paranoid" of his ex discovering their relationship. "He's trying to ensure Makayla stays behind the scenes. She's pretty young and impressionable, so he just tells her what to do and she does it. No doubt she's thinking this could be something serious."

But if Scott's past behavior is any indication, Makayla is in for a rude awakening. "He pretty much behaved like he was single even when he was in a relationship with Kourtney," adds the insider. "So you can imagine what he's acting like now."