Other mistake: When Elvira is being chased by her Uncle Vinnie, you can see the hole in his head from where Elvira throws her stiletto at him. However, the hole in his head is apparent 'before' the scene in which she actually throws her stiletto.
Factual error: Right before Elvira is burned at the stake, the officer pronouncing judgement on her says "By the power vested in me, by the sovereign state of Massachusetts..." Massachusetts (according to its own constitution ratified in 1780) is a commonwealth, as are Virginia, Kentucky, and Pennsylvania. Although the internal governments appear to be different, they have the same legal status as states within the United States.
Continuity mistake: When Elvira is cooking dinner for Bob, she takes the spoon out of the pot, sets the spoon aside, then says her dish looks like "cocka-doodie." When the camera cuts back to the food it looks different, and the spoon is back in the pot. When Elvira puts some spray cheese on the food, the spoon is back where she set it aside earlier.