Finished Rebirth 😌 I think I understand every story event and subtextual narrative theme — BUT there's one thing I'd like an explanation on (hardcore story spoilers)

Why in the Forgotten City did Aerith "revert" back to being stabbed, when Cloud seemingly challenged fate itself by fighting back against the Whispers and parrying Sephiroth's strike? It's like all that fighting against the whispers, and therefore "fate" itself, was pointless. We also know from Remake that "fate" can be subverted, so I have no idea what happened here.