I personally like this change, if that’s the direction The Craft: Legacy goes, because I didn’t quite understand why Rochelle and Bonnie just went evil too.
Based on The Craft: Legacy trailer, it seems like the sequel may take an opposite approach.
It’s shown throughout the movie how Sarah doesn’t want to do bad things and questions their plans and vindictive behavior.
Nancy completely embraces the dark side, and Rochelle and Bonnie join her without much convincing.