When Felicity is trying to help Ben after finding him in the woods, when she crosses in front of the camera, you can see that her riding habit's skirt is actually big-legged pants.
At the Ball, Felicity and Elizabeth dance to Mozart's Eine Kleine Nachtmusik, which was composed in 1787, but the story takes place in 1775.
Shailene Woodley clearly has pierced ears in the scene where she yells at Ben for running away. Not many people, especially children, had pierced ears in 1775, when this film takes place.
Christmas Carolers (if there were any in 1775) would not have been singing "Deck the Halls" in 1775. The English language version of that carol ("Nos Galen" a New Year's song from Wales) did not appear until the 1880s.
When Felicity is in bed after her father announces he has decided to stop selling tea in his store, she says "I've never seen Grandfather so upset" yet her lips clearly say something else.
Williamsburg, where Felicity supposedly was shot, has no curving streets. It is a straight blocked layout.