An anonymous source said the troubled singer allegedly struck Sherene Flash in the eye after the fan asked her if she could take her picture following this week's End of Summer Ball, the Daily Mail reported Saturday.
"Sherene asked Amy if she could take a photo," the source alleged.
"Amy was OK at first, but then Sherene asked if a friend could get in the shot, Amy lashed out."
The source said the 25-year-old, who has had a number of medical and substance-related problems in the past year, had just completed a "tragic" on-stage performance with her goddaughter Dionne Bromfield.
"It was tragic -- she seemed totally wasted," the source told the Mail regarding Winehouse's performance Thursday. "She was jumping all over Dionne as the poor girl tried to sing for the crowd. Amy didn't really sing a single note -- it sounded more like she was grunting down the mic."