i haven't read many fics based on the scorch trials but it seems to me that in the ones i have read, the OC goes from loving teresa to hating her in 1 second.

i understand for the inital reaction to be rage, but understand this: just like a lot of people have different perspectives on different characters, an OC is going to have a very different reaction to the betrayal than thomas, the one who was betrayed. an important aspect to think about is their relationship with teresa, aris, and even thomas, which will help you with writing their reaction to it all. maybe switch it up a little and have them understand where she and aris coming from even if you don't??