Hey,

The only movies I remember that had a chick stuck in a mirror is Candyman... I don't think it was 80s though, and the chick was only in the mirror at the end... Other ideas are: There was a tv show on Nikelodeon called "Are You Afraid Of The Dark?" and I recall an episode featuring a young girl in the mirror... again, not from 80s.... or it might be something to do with Bloody Mary.... the lady in the mirror who comes to get you if you say "Bloody Mary" 13 times into a mirror.... Hmmm.... could be 80s but not sure of movies featuring that character... try looking up horror movies from the 80s and reading their plots....

Good luck!

Mel