She's a bit too stupid, like most manga characters. I think writers make characters that way to make the writing easier on themselves. When they're dumb, the authors can force the plots in directions they want, rather than the direction things SHOULDA naturally happened (following 1+1 logical rules). This whole "catch and release" thing she's doing with the humans right now is a good example of [forced stupidity]. Logically speaking, she couldn't have picked a stupider way of doing things. If she sent the girl to the town's overseer (whichever noble is in charge) with a note explaining that she's not a bad alreune, a chance for dialog would've been made. From there, simply explaining that she lives off of the forest's bounty and has never attacked the townsfolk coulda helped ensure she wouldn't be dealing with an ever-increasing group of enemies. If she explained that she could be useful to humanity by warding off demons that may try to sneak in the territory through the forest, then she could've helped her sitch even more. Her saint magic (after the humans show they can be trusted) has the possibility of getting her national protection. Something akin to what I've written here is the logical and natural route this story shoulda taken.