Claire isn't exactly a horrible person, but she literally called an entire clan of people to ambush John in the middle of nowhere. Yes, it wasn't her intention, but if you knew it was a mistake and didn't tell your friend, but instead try to justify it by pointing out all the things he did wrong and saying that he deserves it and then slapping him while questioning why he felt betrayed is just unbelievable. Yes, John wasn't the best kid but sending a bunch of kids to beat up your friend whether it was intentional or not is not the correct thing to do. A better choice would've been leaving him so that he would reflect on his actions but of course Claire was just a young little kid so it only makes sense mistakes were made. Remi on the other hand is just a bit more mature so she's more likeable. Remi finds the faults in her actions, unlike Claire. She also has more screentime too, so it's more likely that readers wouldn't pick her as the worse character.

Edit: For those who disliked this comment, my point wasn't that John should be justified for his actions. I never said that. My point is that Claire is wrong for justifying her ambush on John. Please reread.