Kendall & Kylie Jenner Beef, Kanye West Fashion Week 'Screaming' Fight? Older 'Know It All' Sister Jealous, 'Fake & Ugly' Plastic Surgery Diss?

Sisters fight sometimes, but rumors suggest that the "competition" between Kendall and Kylie Jenner is now growing way too intense.

Kim Kardashian's beau Kanye West asked 17-year-old Kylie (but not 19-year-old Kendall) to walk in his New York City Fashion Week show for Adidas back in February [2015]. And ever since, the two aspiring models just won't stop bickering!

Apparently, Kendall finds Kylie selfish and immature. Meanwhile, her little sis just thinks that Justin Bieber's rumored "fling" is explosively jealous.

And here's how all the drama started.

After Yeezy honored Kylie with his runway request, she began complaining about her unique outfit choice. Alleged eyewitnesses tell the seedy gossip tabloid Ok! magazine that Kendall tried comforting Kylie, insisting that the wardrobes were pure "art." Supposedly, that "rubbed her the wrong way," and Tyga's younger girlfriend totally freaked.

An alleged source reveals:

"[Kylie] exploded, yelling, calling Kendall a know-it-all and to back off. The whole place fell silent. She went on sniping that Kendall was only there to mess with her head and she accused her of being jealous and trying to keep Kylie out of modeling. Kendall tried to hold back, because she hates making a scene but she eventually told Kylie to grow up and then stormed off."  

Does such diva-esque behavior really sound like Kylie?

Kendall tried blowing things off, but she's still somewhat hostile, too. She knows she's always be "the prettier one" -

"Kendall thinks Kylie looks ridiculous, and she doesn't hold back from telling her so. She also thinks it's grotesque that Kylie has had so much work done particularly at her age," the insider explains. "Kendal was always considered the pretty one while Kylie was totally overlooked. She's been seething with resentment for a long time... Kendall has had absolutely no work done and is flawlessly beautiful... Kylie had everything from butt injections to jaw surgery."

Ouch! Where's the sisterly love? They seemed to be getting along at Coachella just fine...

Should Khloe, Kourtney, and Kim intervene before things get worse?