"Amy does more drugs than anyone I've known," the Sun quoted her as saying.
"I've been with lots of people when they've taken coke, including stars like Lindsay Lohan and Kate Moss. But I've never seen anyone take as much coke as Amy. Even I wasn't that bad," she was overheard as telling a pal.
Courtney also says that Amy "speedballs", taking a deadly mix of cocaine and heroin.
Courtney and Kurt were dubbed "the new Sid and Nancy" in the Nineties, but Amy and her husband Blake Fielder-Civil are the latest couple to take the dubious title.
Amy reportedly suffered a massive drug overdose last month after taking a cocktail of booze and drugs including heroin and cocaine.
She, however, told her pals that she only took heroin for the first time less than six months ago.