A literary construct used by movie screenwriters, especially in the 80s, to help increase the popularity of a movie to the male geek audience.
Although most women in movies are in fact allegories, the nerdy girl allegory is unique in that it is a form few women intentionally aspire to.
Nerdy girl allegories in movies are naturally one-sided, are uncharacteristically unpopular, and rarely show any romantic desire; and when they finally do, it is often with the movie's geek protagonist. The most notable exception being Ally Sheedy's character in The Breakfast Club.
Other nerdy girl allegories in popular contemporary film include Michelle Meyrink as Jordan in Real Genius, Annie Potts as Janine in Ghostbusters, Angelina Jolie as Acid Burn in Hackers, and Rachael Lee Cook as Laney in She's All That. This allegory can also be seen utilized in some 80s and 90s television shows, as with Lori Singer as Sydney in VR5