I am kind of pulling this out of the hat but I really thought about it. Why not the queen of hearts (the alice in wonderland universe). She is known to want to take heads from young girls. It also implicates Tweedle dum and dee. They are innocent sure, but they are working for SOMEONE and I think its to know how much other people know about the murders. Also the "stop laughing at me" could have come from the mad hatter. Probably all of the bad guys wont come from the same story but this is just my theory.
they question of "why" i still cant answer besides possibly getting more power in fable town. while king cole is gone and threatening snows life and eliminating crane (making him flea because of him being a suspect) and luring bigby in to some sort of trap. (See tarot cards ep. 1)
If anyone wants to add to this theory it would be cool to hear what you think about it!