The question is how much Kairi knows Riku did. If, when explaining things to Leon and everyone, Sora conveniently neglected to mention all the EVIL Riku did, and basically summed it up to "tried to save Kairi, he was possessed, gotta save him", then Kairi has no reason to neglect what he's done, especially since she saw with her own eyes him popping up in HB to hold XH back.
But that really depends on if she was aware during KH, what Sora told Leon and such, and as with most things Kairi - it's underdeveloped and never again bothered with :V
You really did like the RiKai fic, didn't you?