The two important things here are things we didn't see. One, Bradford presented no argument along with the Collins history. Here it is: "She has no motive, shows no animosity toward anyone except when screamed at, accused of witchcraft and tied to trees. She's just a mysterious figure. Now that we've heard her time travel story, isn't it possible that this is just one more of the many unexplainable incidents and that she is just one more innocent victim of this series of incidents? How does she not sound like a victim of witchcraft? That constitutes reasonable doubt." At least it's worth trying.
Two, where'd Angelique's body go? [spoiler]Considering what happens in later storylines, either she was transported to Hell where the Devil fitted her with a new body to do his bidding with, then she became a more powerful witch who can physically appear and disappear (unless she did that earlier), as at the trial, then she followed them to 1968 --or-- the spirit went to Hell and was reconstituted, as happens on other occasions I think, going off to 1968... while the body re-animated and healed from some spell she'd cast on herself in life, maybe, she grew a duplicate personality arising out of this healed body, and skipped town, to return once a year to Barnabas's crypt once a year, to see how he's doing, until 1840, with therefore no memory of the future. They never actually explain where the body went.[/spoiler]