"The Man Trap" might be a double entendre. The obvious meaning, as mantrap, denotes something that ensnares a person. In addition, the misogynistic slang term man-trap stands for a woman who manipulates a man, such as with sex (it is used, e.g., in the movie Gentlemen Prefer Blondes to refer to Marilyn Monroe's gold-digger character). The slang term seems appropriate for the form the vampire uses from Wrigley's Pleasure Planet, and also it might aptly describe the way the vampire's Nancy form is used to manipulate McCoy by his fondness for the actual Mrs. Crater.
Makes me wonder what you make of James Blish's title (likely a working title for the earlier draft script), The Unreal McCoy.