I saw two on
YouTube that I love:
1: take here to see Cinderella. When having your picture taken you spy a glass slipper (previously placed with help of cast member). You ask her to try it on and slip it on her foot. After it fits tell her that she is the perfect princess for you and pop the question.
2: you have her take pictures with princesses. Ask them How they make the perfect wish. They will hopefully show your gf how to wish. (get a cast member in on the gig) then when her eyes are closed slip down on one knee with the ring box open in your hand. Ask will you make my wish come true?