I'm still totally unable to get behind the "evil Lucy" theory.
Well.... "Fairy Tail wins" seems to be the most obvious prediction (and from a readers perspective also the most likely) but a draw would be an interesting twist, maybe even a three-way draw? Is it possible? Okay, some quick number crunching say no. Too bad)
As for the princess being dumb... we don't really know how Lucy showed up. Yeah, she might be lying but why would she tell the princess her kingdom is going to be destroyed if not to warn her? Sure, there's no definite proof, but what would be the point if not to help her?
I don't get it.