An actress recalls playing ‘floozies’ on MTV, a bit part on Seinfeld, and more in Hollywood and New York — Back in the 1980s Nancy Balbirer studied acting with David Mamet, who told her she’d be asked to do two things in every role she played: “Take your shirt off and cry.” Mamet may have spoken with tongue-in-cheek, and Balbirer may have tweaked his quote, given that she begins this…