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Staying relevant and having your name in magazines is so fun until an alleged roll in the hay comes back to haunt you.  Life & Style reports that Kristin Cavallari and Scott Disick hooked up in February 2009 while Disick and girlfriend Kourtney Kardashian were on a break (kind of like Ross and Rachel).

“Scott and Kristin hooked up in Las Vegas during a time [February 2009] that he was on a break from Kourtney,” a Kardashian source told the weekly.  “Actually,” another source added, “Scott and Kristin were hooking up on and off for a year, maybe even two.  When Kourt and Scott would fight, he’d party with Kristin and hook up.”

Naturally, the claws came out.  “Kourtney was furious,” the source says (so much gum flapping from this source).  “She and her sisters have called Kristin ‘the whore bag’ ever since.”  The girls were friends prior to their falling out, when Cavallari dated Kardashian’s step-brother, Brody Jenner.

PHOTOS: The Kardashian Sisters Are Thick As Thieves

Then Kardashian found Cavallari on a date with Disick at Apple Lounge in Los Angeles in April 2009 and it all went to sh*t.

Cavallari, who is back with ex-fiance Jay Cutler, denied that she ever hooked up with Disick on The Billy Bush Show yesterday (November 16th), according to Us Weekly: “I just think, what convenient timing for them with their show premiering next week. With everything that’s going on for Kim, I feel like they’re trying to take the heat off her,” Cavallari said of the reality family. “When there’s a big story like that, they always call you and ask if you want to comment and clearly none of them denied it.”

Cavallari then added, “It’s disrespectful to me and Jay.  And I think it just says a lot about their character.”