[quote=@Rune_Alchemist]
Would they not accept a cease-fire? They wouldn't be helping the dark girls or the monster girls, but they wouldn't have to attack them either. 
[/quote]

I think the problem here us getting the more zealous parts of Beacon to agree to a cease fire too. That's the problem of being in a large organization, and Alicia certainly can't guarantee that someone wouldn't act of their own initiative. 

Now if the monsters/dark magical girls/horrors were willing to maintain good behavior amongst themselves by force there might be some place to go, but somehow I doubt anyone is going to agree to that.