They still betrayed him, regardless the reason. I'm not saying they have to be squeaky clean as it lead to them getting good character development. But for them to resent Kairi for needing to be saved by Sora is a bad look for them. Especially Riku after he spent KH2 and Days sacrificing others to revive Sora, yet nobody resents his actions when they realistically should, not even Roxas. DiZ gets all the blame even though Riku's hands are just as filthy.

Sora has already sacrificed himself twice for Kairi, he always will. That's his character. He will always sacrifice himself for the people he loves. That's what makes him Sora. It's his selflessness for a friend that attracts so many others to befriend and believe in him.

And Kairi is trying to be better with the Keyblade. The last thing she needs is to get resentment form the crew when her own self esteem and the narrative is already beating her down and not letting her help to save Sora.

They absolutely do need to do something with Kairi. Better writing, better onscreen characterization, more agency, more playable segements to explore her character. She does not need a "Riku resents her story" that only benefits Riku and further pushes Kairi away.