the real question is how did kairi get to destiny islands pretty much imediatly after bbs?
while we're at it, lets ask some more paradoxes!

(SPOILER)
how did beast get to hollow bastion?
why isn't rikku the hero when he is linked directly to terra in bbs, but sora isn't but barely linked to ventus?
why is neverland in EVERY kingdom hearts game except 2?
why is agrabah changed so much in 1 and 2, same with halloween town?
how does merlin live in radient garden but without it being completely destroyed he is in traverse town?
Why is Sora voiced by a girl?
how and when is re:coded supposed to take place?
How does Sora grow over a foot in a year?
why is Roxas Ventus?
How is it that terra goes to cinderellas castle after ventus, but is at the dwarf woods before ventus, when that is the first place Ventus goes????????????????
the answer to all of these is: I T I S A G A M E

Edit: Mark your spoilers -Murder