@Ewario Honestly I like that she didn't attack the village. I mean it doesn't really benefit her much to just destroy it. Leaving the town alive gives her a place to easily collect resources in both meat and information on the local area, keeps a force there that doesn't know she exists so she can manipulate it for her use in the area, and destroying it risks revealing her to whatever kingdom owns that town that could just send a force too massive for her to take down right now as she has is in the early stages of building her army. I see her not just raizing the city as a good strategic move and better displays her command skills.
The way I see it, right now she is only attacking those that directly attack her. She is not attacking these criminals gangs because she is trying to be good but because they have angered her for having the gall to try to take her as a slave and kill one of her minions. If they don't attack her, she'll either ignore them or use them for any advantage they can give her. It kinda reminds me of the borg from Star Trek where they will completely ignore you until you attack them since you are so inconsequential to them that you are not worth the effort to deal with. Also the swarm doesn't seem to sadistic to kill without reason; though those reasons can be petty like not showing proper respect or providing what they desire. Though I do see her going to war with the humans eventually if the mistreatment of elves is not only done by the criminals but by all humans.