OK! Exclusive: Kim Kardashian “Jealous As Hell” Of Kendall Jenner—Find Out Why!

Kendall Jenner has it all—a great modeling career, business deals with Estee Lauder and PacSun, tons of famous friends and much more—so it’s no surprise she attracts all sorts of jealousy. But the 19-year-old has a new jealous hater to add to that burn book: big sister Kim Kardashian!

An insider close to the family told OKMagazine.com that the 34-year-old is envious of her sister and is worried she could end up out of the spotlight for good now that Kendall is such a hot topic! Worst of all, the source said they’re fighting up a storm and it’s getting nasty!

PHOTOS: Kendall and Kylie Jenner's Most Scandalous Instagram Pictures

“Kim is particularly jealous of Kendall and has it in her head that she’s taking a ton of business away from her, so the knives are really out," the insider revealed to OK! exclusively. “They’ve had a lot of tensions recently, but the money-spinning Estee Lauder deal really pushed Kim’s buttons and she’s jealous as hell.”

But Kendall is no victim of jealously—she’s fighting back! The model had some harsh words for her sister, particularly about her “over-sexed antics” and her recent Paper magazine photo-shoot, calling it “cheap and nasty.”

PHOTOS: Kim Kardashian's Most Naked Instagram Pics

“It’s very ugly between these two at right now, and Kendall’s alienating most of the family with her self-entitled, Queen Bee attitude,” the insider added.

Last week, OKMagazine.com reported that Kim was starting to get worried that she may no longer be the most relevant Kardashian since Kendall started becoming an “IT girl” in the fashion industry. So that led her to do the nude photo shoot and gain back her cred.

“She wanted people to be in awe of her body, not slamming her for being an irresponsible mom,” a source said. “But Kim will do whatever she has to do to stay relevant.”

PHOTOS: Kendall Jenner Takes Fashion Week: See All Of Her Runway Moments

But Kendall has a semi-nude shoot of her own now, proving these sisters can’t stop trying to outdo one another! The second-youngest Jenner girl posed in sexy lingerie for Love Magazine!