Kylie Jenner skipped sister Kendall's 19th birthday party at the Hotel Bel-Air on Monday, and rather than celebrating with her family, the youngest member of the Kardashian-Jenner clan went to a hair salon in Beverly Hills!

Kylie didn't even wish her older sis a happy bday on Instagram or Twitter, but she did find the time to post a selfie of her new extensions. Glad to see she has her priorities straight!

So what's the possible beef about? "It is a competition between them now as to who can be the more famous Jenner and it is destroying their relationship,” a source close to the family tells Radar. "It’s sad. They used to be so close and now they are really letting this fame thing affect them!"

The insider added:
    "She thinks that her music career is going to take off and says she is getting her name out there right now. But it’s just another way of her trying to one-up Kendall. Kylie feels like Kendall abandoned her when her modeling career took off. And she kind of did. That’s why Kylie has gotten so close to Khloe recently. Khloe is the only one that keeps it real anymore."

Sounds like Kylie is just jealous of Kendall's success in the fashion industry! Maybe the 17-year-old reality starlet will finally make something of herself when her album comes out? We can't WAIT to hear that!