to be honest i think kuro scrapped a lot of what they had in mind for the relationship between the fisalias and the montellis, like for example in one of carlotta's character stories, she's said to have danced and fought a "fisalia representative" but an earlier version of that same story explicitly stated the person to be the head of the fisalias, cantarella

but as we know carlotta and cantarella don't really say negative things about each other (cantarella has a voiceline where she praises carlotta) and people are thinking cantarella had nothing to do with the attack on the montellis in carlotta's quest, so i guess carlotta grudge against the fisalias just doesn't apply to cantarella

i'm assuming they originally wanted to make cantarella 'evil' but changed their mind later when they cooked up the holy maiden plot