A source tells PEOPLE that Disick "really screwed up, again, and the entire family knows all about it"

By Emily Strohm; Steve Helling and Melody Chiu
Updated July 29, 2015 07:00 AM
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Credit: Gabe Ginsberg/Getty; Alo Ceballos/GC Images

Scott Disick has made plenty of mistakes on and off the camera, but after the Keeping Up with the Kardashians star was photographed kissing a blonde in Las Vegas on Friday, he may have ruined any chance for reconciliation with former girlfriend Kourtney Kardashian.

After the mom of three, 36, dumped Disick last month when he was photographed cozying up to another woman, a source tells PEOPLE that Disick, 32, had a moment of clarity and “started talking about being the father he was supposed to be” to their kids Mason, 5, Penelope, 3, and Reign, 7 months.

But before he had a chance to make things right with his longtime love, Disick made another bad decision, the source says.

“It was like he undid all his progress from the past week and then some,” adds the source of Disick’s PDA with the mystery woman. “He really screwed up, again, and the entire family knows all about it.”

Despite the drama between the duo, a source close to Kardashian says this may not be the end for the couple.

“For the first time, she’s taking a hard look at what her new reality could look like,” the source says. “Before, she just assumed nothing would really change, but now there’s a strong possibility of life without him and that’s a scary thought for her. She’s figuring it out and taking it as it comes.”

For more on Scott and Kourtney, pick up the new issue of PEOPLE, on stands Friday