for Princess Nevermore by Dian Curtis Regan
As living in an underground kingdom has become predictable and boring, Princess Quinn of Mandria dreams of visiting the upper Earth-which she can see via a magic pond, the only portal of light and outer life in Mandria. Cam, the wizard's apprentice, tries to use his magic ring to transport them to upper Earth, but the spell only works on Quinn. Is Princess Quinn lost forever in the outer world? Or will the desires of her heart bring her home again?
Publisher description retrieved from Google Books.