Even flashing requires a little practice. Not doubt even the most experienced flashers started out doing it in front of a mirror. To make sure their clothes opened as quickly as they needed them too. You're seeing Liza do a little practice. Warming up for flashing on the cold snowy winter scene. Only when she feels comfortable she goes outside to flash. When everything is ready and she's good to go. She is looking to have the maximum impact when she flashes. If the guys around her don't freak out, she doesn't feel like she's done a good job.