Add one more item to the list of things Regina Lasko has against hubby David Letterman. The Late Show host brought galpal Stephanie Birkitt along on vacations with Lasko and son Harry, sources tell the New York Post. Other friends and coworkers were also invited along; one of the trips was to St. Barts. Lasko, also a former Late Show staffer like Birkitt, “has to be really, really pissed,” the source says. (More David Letterman stories.)