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...Nobody can tell Britney what to do anymore. No one can control her. She is a mess." 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 dance number was spectacular - without her," said our spy at rehearsal. "When the stand-in was rehearsing with the dancers, in the hours they were all waiting for her, it was amazing. Then Britney showed up and refused to do anything. 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." Meanwhile, Spears was agitated because she didn't like the outfit MTV had selected for her. "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. MTV execs weren't the only ones worried about Spears' impending debacle. Another spy said, "The dancers were texting pals, asking them to pray for them. They were worried." 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."