The 'Since You've Been Gone' singer reportedly sank a bottle of liquor with
Ryan Key - the singer of US band Yellowcard - at the Metal Skool concert at
the Key Club before jumping up on stage.
A shocked onlooker told the New York Post newspaper: "She ended up tearing
off her vest and throwing it into the crowd before playing a lot of air
guitar."

One fan says, "She really can sing. She belted out these songs and really stunned everyone.

"At one point we all thought she would bare her breasts but she simply took off her sweater. It was a real hoot watching a Miss USA-type downing whisky with a sleazy rock band. She was having a great time."

Meanwhile, Kelly, 25, has been ordered to slim down if she wants to front a
new healthy drinks campaign.
The 'American Idol' winner has signed a contract to promote her favorite
flavor of Vitamin Water but bosses at Glaceau, the company that
manufactures the drink, feel she needs to lose some weight before they use
her to advertise the beverage.
As a result, Kelly has been put on a strict all-organic diet and has even
hired a professional chef to prepare all her meals while on her 'Addicted'
tour.
Kelly recently revealed how she considers it her responsibility to send the
right message about eating to her fans.
She explained: "Obviously, I have a lot of young fans. I just realized that
I have a platform. If you have a voice, you might as well make it a positive
one."