>>712681787
It's ambiguous on purpose. Noelle was supposed to be the girl, school fountains were prepared for her, but Susie blundered into supply closet and Kris and Ralsei decided to go with it in hopes of breaking the prophecy.
Speaking of, I've been replaying chapter 3 just now, and when Shit Squad walks in on Tenna speaking on the phone, Tenna specifically says "If that purple girl finds out about this, it's ALL OVER!" So Kris and Ralsei are both in cahoots with Knight.