Kairi thinks:

Riku is silver and beautiful, and his eyes watch dreams. She thinks they speak to him, now, too; the distance in the tilt of his head is calmer than it used to be, when he was straining to read their lips.

She does not tell this to Sora. Sora would demand that Riku's dreams give him back to them. Sora's dreams only ever make him more where he is.

Sora's dreams live in his heart. Riku's live in the sky.