she once got betrayed by her own family, she thought they were genuine, she thought they love her bc she trusted them so much but she got betrayed in the end, she got killed and turns out his father was killed too, ofc after all that she would have a trust issues regarding ppl, fl has her own trauma
i don't think she was completely shutting off, i think she just needed some time to rethink her actions cuz she was too traumatized by her prev family. and to be fair, theo did keep a lot of secrets from her and she must've felt frustrated for all of that. as kind and gentle theo was to her, what she needed from him is to be able to trust him and for him to trust her. i think the confusion was necessary cuz they needed to fight and get those emotions out to really say what they feel (=・ω・=)
I honestly feel bad for the ml. All his actions up till now show that he is a good person. Hurt and traumatized but good. But the fl heard a story that was clearly twisted to make him and his family look really bad and it immediately made her question everything. Like it's so easy for her to not trust him. This is so sad.