Dolly had no braces - explained.
So this is my theory on why people think they remember Dolly having braces - and I would think many other "Mandela effects" have a similar explanation.
When Jaws meets Dolly, there IS something cute and clever about the scene. It's that HUGE Jaws has found his love in such a TINY girl.
But in the back of everyone's mind, or maybe talked about later with friends, everyone agrees that the scene would've been perfect and more cute and clever had Dolly worn braces.
Then years later when you watch the movie again, the scene is approaching where Dolly is walking up to Jaws. You think "Oh yeah I remember this - there's something cute and clever about this scene. Yeah watch, she's gonna have braces."
It's just a false memory, folks.