It looks like Rihanna isn't quite up to speed on one of the most important things all girls learn in middle school: chicks before d**ks!

While RiRi spent last year's Grammy Awards seated next to her BFF Katy Perry, things were a bit different this year, as the old friends steered clear of each other the whole night.

The reason? Katy (like so many others) totally hates the idea of Rihanna rekindling her relationship with Chris Brown!

"They aren't tight anymore because Katy doesn't approve of Rihanna dating Chris Brown," a source tells Us Weekly. Because of this, the ladies were seated separately in the audience, where Rihanna snuggled up to Chris and Katy spent time with her beau John Mayer.

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Of course, Katy isn't the first person to criticize Chris and Rihanna's relationship. This is the first time, however, that we're learning RiRi has actually lost a friend over the scenario. Not good!

However, Rihanna stands behind her decision to take Chris back after he was arrested for assaulting her in 2009. "He doesn't have the luxury of f---ing up again," she explains.

Do you think Katy should totally cut Rihanna off because of her relationship?

Photos Courtesy of: Getty Images