Yep, we're spoiling another game, this time one that's eleven years old. So, don't click the link if you don't want one of a decade-plus game's pivotal plot points revealed.
Aerith is one of the main characters of the game, and a driving force for your quest. She's the last of her race, the only hope to save the world, that kind of thing. Imagine the shock and horror of millions of players when, a good way through the game, she gets murdered. Permanently.
It's pretty unexpected and actually pretty brutal. Especially when you've spent hours and hours building her up, and getting to 'know' her character. This kind of led people to wildly speculate that she could be revived. That there were 'clues' everywhere.
But, these are all red herrings. She's dead and there's no bringing her back. And the reasoning is pretty simple, really. If you could bring her back from the dead, then her death would be meaningless. She may as well have just taken a nap for a few weeks of game time which just doesn't have the emotional impact, you know?
So go ahead and get all your characters to level 99 if you want, run the clock up until it stops, and then take your airship and fly around the planet 30 times in a row. All that will do is make you bored, and dizzy.