[Shadow5YA]

Originally Posted by Kanon

Spoiler for Ending:

Aerith is dead now. The situation has changed, Cloud is needed to stop Sephiroth. And I don't think she knows he has the Black Materia, she was hanging around the others when Cloud realized he had it and he quickly hid it inside his sword.

Nanaki sensing her right when she tries to touch him completely excludes the possibility of her being a mere hallucination. It's too big to write off as coincidence.

It's also highly likely that after dying and becoming one with the lifestream, she regained the memories/visions from the future the Whispers took away at the end of Remake, so she knows how instrumental Cloud is in bringing down Sephiroth and can't just let him sit this out like she had originally planned.

Spoiler:

What has changed? Aerith was praying to stop the Meteor and still is. Her job didn't change even after she died and she knows it.
The situation only changed for Cloud's party because they don't know exactly that Aerith was summoning Holy and thought she failed the moment she died.

Also if the Aerith in the ending had knowledge of the future, then she would've known that Cloud has the Black Materia and that Sephiroth can't summon it yet. You can't have it both ways where she knows the future but doesn't know where the Black Materia is at the same time.
The simplest reason why is that this Aerith only knows what Cloud knows.



The Aerith who does have knowledge of the future - the alternate timeline one who gave Cloud the Holy materia, and the one who told Cloud she wanted to find the "real" him, disappeared by Cloud's side after the fight with Sephiroth. We may see her again, but that's not who's talking to him now.