Mean Girl! Kim Kardashian Snubs Chris Brown's 'Lowbrow' Girlfriend Karrueche ...

Is Kim Kardashian a Mean Girl?

RadarOnline.com can exclusively report that the reality star, 34, threw a diva fit when Chris Brown's on-again model girlfriend.

Karrueche Tran, 26, requested that they take a group picture together with their men at singer Teyana Taylor 's listening party in Hollywood this week.

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'Kim said absolutely not and turned her down,' an insider tells Radar.

However, when Brown, 25, asked Kardashian's hubby Kanye West, 37, for permission to take the photo, the rapper happily obliged- leaving his wife with no choice but to participate.

'Kim cooperated, but made it very clear she was not happy about it,' the insider adds. 'She acted like a complete b*tch. At one point, she even walked away while Karrueche was talking to her.'

The source claims there's no bad blood between the two women; Kardashian simply thinks Tran is 'lowbrow.'

'It was clear she believes she's better than other people,' the insider explains of the former sex tape star.

It looks like the 34-year-old mom of North, 16 months, has gone from the victim to the bully. As Radar reported this spring, superstar Beyonce, 33, ignored Kardashian at a Los Angeles doctor's office, and even flaked last minute on her over-the-top Italian wedding to West in May.

'Beyonce wasn't going to allow a Kardashian to socially climb her,' an insider explained to the New York Post.