I've been thinkin' that Kairi lost her heart at KH1.but the rest of the Princesses of Heart did not.At least,they had their hearts when Maleficent opened the Final Keyhole.Maybe they lost them when Riku created the Dark Keyblade.Remember when Sora stubbed himself?The Dark Keyblade vanished and left the six Princesses' Hearts behind (which then returned to their owners).Now...my theory is that the same thing that happened to the six Princesses happened to kairi as well.is it possible that the princesses of heart have all created nobodies??
"The Dark Keyblade/Artificial/Heartbreaker"
"The Dark Keyblade/Artificial/Heartbreaker"