The Aerith vs Sephiroth conflict is so interesting when you look at it from a more meta perspective.
We, the fans, are Aerith. We know all the big plot twists already. We know she is supposed to die, but we are desperate for her to live (we even rewrite the story in our own ways to make it so she does live in fanfics, AUs, etc). As the events of the remake trilogy diverge further and further from the events of the original, of what we know is supposed to happen, we lose our certainty of what else is to come. It gives us false hope. Or maybe it scares us, the uncertainty and divergence from what we know makes us uncomfortable.
And then there's Sephiroth, the writers. They killed her in the original timeline and they will kill her again. She needs to die for their ideal story and they bend the fate of the world to their will to ensure it will happen again and again and again. There is no true, canon universe where she survives the journey and they will ensure that. That won't stop them from playing mind games with us though.
Sephiroth will say and do things that only us (and Aerith) understand the true meaning of. Every other character is ignorant to the true conflict going on between the two.
He taunts, lets this false hope dwell within both us and Aerith before converging different timelines to make sure Cloud can't save her, killing her in every universe.
And then, after she dies, both her and us watch as the rest of her friends continue on without her, yearning for a world where things were different. But that world doesn't exist, and it never will. Because Aerith was never meant to survive.
