That really would be a problem huh? The majority of the group will be in roughly one place, but "Blue" goes to a different school. If it happens at the school trip area, that's a lot of opportunity for random people to get dragged into it or witness them. If it happens over by Blue, she's on her own. Since this is a story, I'd usually say there's like a 99.9% chance Blue is the next one exactly because she's supposed to be alone during this time's blackout. But the potential uses for having it happen near the bigger group, or even coming up with some way for Blue to go along with them, takes the edge off of that. Maybe 75% in favor of Blue, 25% in favor of the school trip group.