You know, MC, there's a very easy solution to this all - just kill her. Doesn't solve the problem you say? Yes it does, you braindead imbecile. And you won't get into trouble either, since you don't have to kill her yourself, you can use the summoners as your pawn, so all she will think is that she got betrayed. And lo and behold, all's well. Heck, kill the king while you're at it.