Kourtney Kardashian and Scott Disick - People Magazine

Kourtney Kardashian and Scott Disick - People Magazine

Kourtney Kardashian and Scott Disick

Denise Truscello/WireImage

By Aili Nahas

07/08/2015 AT 07:00 AM EDT

Over the course of their nine-year relationship, Kourtney Kardashian and Scott Disick encountered more than their share of bumps and bruises â€" many of which played out for millions on Keeping up with the Kardashians. But over 4th of July weekend, when photos emerged of an apparently inebriated Disick cozying up to another girl, Kardashian reached her limit.

"It was the last straw," says a source close to the former couple. "Things were rough beforehand, but Scott was supposed to be taking some time to process things, presumably with the end game of fixing their relationship."

Instead, while on vacation in the south of France and Monte Carlo, Disick, 32, "got out of control": "He wasn't trying to get it together. It was more of the same," says the source.

And, after years of weathering cheating allegations, rehab stints and more embarrassing public displays of drunkenness, Kardashian, 36, was fed up.

"Kourtney knew he was going on the trip. They both though this could be a chance to breathe and work on things," says the source. "She didn't mean that he should be rubbing lotion on another woman's back."

Now, as the parents of Mason, 5, Penelope, 2, and Reign, 6 months, begin to navigate life apart, friends of the former couple lament the fact that the relationship ended the way it did. "The bottom line is Scott threw this away," says the source. "It's too bad."

• With reporting by STEVE HELLING

RELATED VIDEO: Kourtney Kardashian and Scott Disick Have Ended Their Nine-Year Relationship

For more on Kourtney and Scott's split, pick up this week's issue of PEOPLE, on newsstands Friday

Kourtney Kardashian and Scott Disick - People Magazine
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