Demi Lovato - Heavy Drinking, Drug Issues Led to Rehab ?

A new report from Life & Style magazine suggests that Demi Lovato was abusing alcohol and cocaine prior to being admitted to rehab, and heavy drinking and drug issues contributed to the Disney star's final breakdown.

A Texas college student named Brian Payne claims he saw Demi doing lines of cocaine like a pro at a party in Texas on December 28, 2009.

"I just remember her doing it as if she had been doing it for a long time. It didn't seem like something new to her," Brian tells L&S, recalling the wild party they attended after a concert by the band Neon Indian at the Granada Theater in Dallas.

Now a second witness at the same party is confirming that story telling RadarOnline.com that there is a video of Demi using coke and the video is being shopped to various media outlets.

"Demi was belligerent, being slutty and doing coke all over the house. The guy who hosted the party shot multiple videos of this and what I've seen with my eyes, Demi is screaming, '[expletive] all of you, I'm famous, I don't care what any of you think of me the whole world loves me.' He shot her in the bathroom as she was finishing a line (of cocaine)."

Demi's rep flatly denies those claims. "Demi Lovato is not in treatment for drug or alcohol addiction. As we have said since she entered treatment last week, Demi decided to seek help for emotional and physical issues she has battled throughout her life," the rep said in a statement.

Demi is currently receiving treatment at a rehab facility outside of Chicago. We wish Demi a quick and full recovery.