Zelda and Midna are both female rulers of their people. Therefore they are both Queens not princess', Queens! I understand that while Zant was ruling twilight Midna was a Princess of sorts, but in the end she's a Queen like Zelda!
It's very silly of me getting so annoyed over it but I don't have a life so why not post all my most serious problems!! I'll also admit Twilight Princess sounds a lot better than Twilight Queen.