An all-out celebrity girl fight has broken after between Kirsten Dunst and Mary-Kate Olsen, after the actresses were spotted exchanging unpleasantries during a wild night out in Miami’s South Beach last week.

The girls, who were in town for THE Art Basel Convention, reportedly got into a nasty spat while sitting together at The Audi Party at the Delano in South Beach last Wednesday night.

“They just kind of stared at each other for a long time and then started exchanging nasty words,” says an onlooker. “Then Olsen just got up and left. She’s been going really late every night.”