OK she’s veeeeery stupid from the start, but it was ok as she at least TALKED everything out, and it could be explained by her overprotected upbringing… here too, it can be explained, she has no reason not to trust the guy BUT the succession of events and attitudes (both him and his sister) should make her at least a little suspicious… Actually she has a very small clue in her very small brain and we see that in her toughts…. but still… can someone be THIS stupid ??? (nono it’s not naïvety here, it’s plain stupidity… for story purpose ^^ )