Answer: In the drugstore
Becca quickly opened a bag of salt and made a salt ring. As she poured the salt, it glowed blue. By doing this, Becca and Izzy were protected. When Winifred tried to cast a spell on them, it ricocheted and the teens were able to escape. When there were hints of magic happening, you would see a blue glow. She did show magic in the dungeon, garage, and in the final forest scenes, but the drugstore came first.