true calling
As soon as the game starts, we learn Kairi's true home is not Destiny Islands, which is the trio's motive for leaving the island in the first place - the fact there are most definately 'other' worlds out there. Destiny Islands itself is a group of.. islands, one where the main town lies, and a smaller one that the children have proclaimed as 'theirs' and play there everyday. The main island seems to be more like an everyday community and village, even having a school of sorts.The recent she went there in the first place was because Xenahort sent her there, making her a selected Princess of Heart. It was to see if she could get close to the keyblade master, which, the experiment worked. However, not too well, since when the islands were destroyed, Kairi's heart was taken along with it.
For Kairi, the islands are her home. Since she doesn't know about her past life in Hollow Bastion till quite late on, she treats Destiny Islands as her home. Even in the second game, she goes back there to wait for Sora and Riku's return. She never questions her past life, not once, and doesn't seem to have an ambitions to go and visit or go back to Hollow Bastion. Perhaps, because Destiny Islands is a more special place for her. She grew up there, with her friends. However, it could also be since that's the place Sora will come back to, so obviously she wouldn't want to be someplace else when waiting for his return. In this branch of the game, it's always possible she might visit Hollow Bastion. But then again, she'd probably still remain on the islands - there's not really anything left for her Hollow Bastion.