I think the suggestion of Aurora from Larkub couldn't be more perfect for you! It's old fashioned, unique and princessy all at the same time. It is too girly for my taste as I also like names with a tomboyish vibe but the nickname Rory is perfect to give it that unisex edge (also makes me think of the cool pretty girl in the Gilmore Girls). A few other suggestions:
Tabitha nn Tabby or Tibby
Matilda nn Mattie
Penelope nn Pip
Scarlett nn Scout
India nn Indie
Ivy (in my opinion old fashioned, flower name but would really suit a tomboy as it's less fussy than the other flower names)
Theodora nn Thea, Dory or Teddy
Florence nn Flo
Cosette nn Coco
Francesca/Frances nn Frankie
Belle (classic, princess, mmore unique than the other belle names and not overly frilly so could suit a tomboy)
And if you wanted something more unsusual (a very random list!)...
Briar (princessy after sleeping beauy's real name but more unisex)
Cleopatra nn Cleo
Minerva nn Minnie
Clementine nn Teeny
It might be hard to find a name that is princess and tom boy.
Suggestions princess/girls names :
Charlotte nn Charlie?
Old fashioned... not sure which period you mean to me old fashioned is Constance Margaret... Winifred Edith... Margot Agnes... Dorothy June... Ida Hazel...
I could go all day so will stop now
What about a goddess name? It would be both old fashioned, and sort if priness sounding (:
My favorite is Gaia (GUY-ah) which means 'Earth Mother'. This name has history, yet it doesn't sound old either (:
Good luck finding the perfect name!