Rick Dembow January 28, 2005 -- A stunning 28-year-old actress died in her fiancé's arms yesterday after a Lower East Side thug answered her challenge — "What are you going to do, shoot us?" — by firing a single bullet into her chest, cops said. Nicole DuFresne, of Brooklyn, had just left a trendy bar with her fiancé and another couple when they were confronted at about 3:15 a.m. by four muggers — two men and two women — at the corner of Clinton and Rivington streets, police said. One of the thugs, who was carrying a gun, demanded money....