Britney Spears is a professional

Page Six has a long explanation of everything that went wrong with Britney Spears’ performance at the MTV Video Music Awards Sunday night, including the fact that she showed up hours late and out of shape to rehearsal, had a drink in hand, and refused to wear MTV’s outfit because she thought it wasn’t sexy enough.

On Saturday, the day before the VMAs, Spears was scheduled to arrive at rehearsal at around 1 p.m. Our spy said, “She didn’t even get to Las Vegas until 4:30 p.m. It was ridiculous . . . The production people at MTV were freaking out.”

To make matters worse, when she arrived in Vegas, Spears didn’t go straight to rehearsals.

“She went to her hotel room and ordered a bunch of food and some frozen margaritas,” the spy said. “She came down, like, an hour later with a frozen margarita in her hand.”

When Spears preformed on Sunday, she stumbled a couple times and couldn’t remember the words she was lip-syncing. She covered her mouth at one point but by the end of the song had simply given up any pretense of singing.

“The dancers were supposed to lift and twirl her in the air a few times, and that just wasn’t going to happen. The more complicated dance moves had to be erased because she couldn’t do them. MTV wanted her to wear a corset outfit. It would have looked great and covered a lot of things up, but she hated it and didn’t think it was sexy enough.”

Instead, Spears changed into a spangly bra-and-underwear outfit she’d brought with her that emphasized her weight gain over the last year.

After Spears performed at the VMAs, she allegedly broke down in tears but then partied until 3 a.m. She changed outfits several times and again was photographed by paparazzi wearing no underwear.

To be fair, that other outfit probably would’ve covered Britney up. And how is Britney supposed to show off her sexy body if she’s covered up? God, sometimes people don’t even use their brains. It’d be like covering up the Mona Lisa. Assuming, of course, the Mona Lisa ate a bunch of other paintings, was always asking for bacon, and was planning on shuffling around on stage for three minutes before collapsing out of breath.

NOTE: If you haven’t already seen it, I put up the video of the crying Britney fan that’s been circulating the interweb. And yes, it’s fake. I mean the guy is real, but the stuff he says is not. His name is Chris Crocker and this isn’t the first ridiculous piece of acting he’s done on YouTube.