If you look for it on the Internet, you can find pages for highly popular movies which show you all of the mistakes present in the movie. The wrong props used, things left exposed that shouldn't show, etc. You are aware that as that being a movie, she did not really wear braces. They were just part of the 'costume'. I think that was just to show her as turning into beauty from awkwardness and was done deliberately. She and Jaws had been selected as part of the perfect crew to become part of the new world population after they destroyed the population of the old one, the thesis of the plot. Star Wars had a myriad of technical details left in error, like space ships where they should not and could not have been.
In case you had not noticed, movies are NOT for real. Large productions have a special position which is referred to as continuity or script supervisor who is supposed to stop errors like this from occurring, but they still do so, although this seemed clearly to be deliberate. https://en.wikipedia.org/wiki/Script_supervisor