We know there is an evil group manipulating the guild, but her and her band being murder happy nutbars doesn't give me faith in the whole "good of the world" they keep spewing. (Honestly makes them seem rather culty themselves.)
I also agree with others, if the author tries to make her a good guy without any issues - gonna be pissed. God forbid she talks or uses any reasoning, nope... She was told to murder folks for the greater good (insert Hot Fuzz clip here) and happily went off to butcher children for her goals.
Being a childhood friend seems to be a license to kill in alot of these manga, and it frustrates me.