Towards the middle of the movie, almost all of the characters are in the house for last minute decisions and preparations. The bride-to-be apparently could not make up her mind as to which hairdo suited her best because it makes several screen to screen changes - headband, no headband, barrette - you get the picture.
This slip-up is so obvious, I don't know how the editors didn't catch it! Of course, I have seen the movie NUMEROUS times, and only saw it after it was pointed out to me.......good eye!
I see this everytime I watch the movie, and it absolutely drives me crazy! You'd think that since they obviously filmed that scene on different days or times or whatever, that they'd have styled her hair the same way.