*Despite a public brushing off her husband Robin Thicke’s sexualized performance with Miley Cyrus at the MTV Video Music Awards, TMZ is reporting that privately, Paula Patton felt humiliated — and it set in motion the path to their separation.

Sources connected to the couple tell TMZ that Patton felt “utterly disrespected” when Robin virtually simulated sex with Miley on stage. After the performance Paula reportedly got into a blow-out argument with Robin, telling him he insulted her before a huge national TV audience.

What really pissed Paula off is that the performance was a total surprise, notes TMZ. Miley improvised the raunchy part without warning, but Robin played along … and that enraged Paula.

Sources say Paula also became irate when she saw photos surface of her hubby at one of the after-parties cupping a woman’s behind.

“We’re told things never got better after that,” reports TMZ. “They argued constantly and Paula was furious Robin continued to party at clubs with various women … pictured at times getting very cozy.

“It reached the point of no return last week — at least for Paula. As we reported … Robin is pulling out all the stops to change her mind, but we’re told she wants out of the marriage.”