The Olsen twins had the backstage W Suite closed off to the public so they could party in private - only to sit around looking miserable.
A source told the New York Post newspaper: 'They weren't drinking, they weren't talking - not even to each other. They sat in silence for at least 20 minutes, staring at the floor.
'They looked like the saddest people you've ever seen.' Mary-Kate and Ashley - who first appeared on screen when they were just nine-months-old - have built up a multi-million dollar brand name as the 'wholesome Olsens'.
But onlookers attending Fashion Week said neither Ashley nor Mary-Kate - who has battled an eating disorder - were looking happy or healthy.
The source said: 'They were wearing heels bigger than their waists.'