Continuity mistake: After Winifred, Sarah, and Mary get off the bus, when the young girl dressed as an angel stops and says, "Bless you," the candy bag she's holding switches from her left hand to her right arm, then back to her left hand, between shots. (00:48:10)
Continuity mistake: When Dani and Max wake up, the sun is out, and they say it's "5:00am," but when they go upstairs and Dani is caught, it's dark outside again.
Other mistake: The same footage of Allison making the salt circle in Max's room is used both times we see her do it.
Continuity mistake: As Alison holds off the Sanderson sisters with the box of salt, some shots show her holding the salt up close to the Sandersons while other shots the box of salt Is further away from them.
Continuity mistake: When the witches figure out that the "Burning Rain of Death" was actually water, it showed that they were all wet from before they managed to get under cover. In the next shot, as they leave the house, they're all bone dry.
Continuity mistake: When the sisters are in "Satan's" house and meet the wife, her curlers change position.
Answer: They were set up, beforehand, just in case. Winnifred knew about the spell, but she didn't memorize the incantation. So she needed the book to see how to cast it.
Phixius ★
If you pause the movie, you will see that the book opened up to the Black Flame Candle spell.