"So did anyone consider that Aerith is from the future?
AC established that Aerith can do what Sephiroth can do. Sephiroth created avatars to interact with Cloud in AC (Kadaj and so on) and in Case of Lifestream, Aerith said she can do that too but chose not to.
If Sephiroth really came from the future it's possible Aerith went back too. So her consciousness is in the past Alt timeline Aerith's consciousness. But then she'd know that the Time Janitors are there to keep everything the same. So she's not really any better than Sephiroth - she also wants a second chance. Except she wants a second chance at a happy ending even if it means the planet might not survive this new timeline....
I'm saying this because of the scene Aerith picks up Marlene from the bar. Marlene seems to have some kind of vision and Aerith puts her finger to her lips to say 'don't say anything'. Like don't spill the beans. So she definitely knows what her fate will be and she's willing to risk the planet's eventual happy ending so she can have a chance to live again..." --
ShawnandAngela
"As someone who has read the script I’ve been thinking this theory for months and just waiting for someone else to bring it up. Yes, I 100% believe the Aerith we see in the remake is one who has chased/followed Sephiroth from the future and is there to stop him in every sense of the word.
There are other scenes that imply it, too. Like, when Aerith asks Cloud to be her bodyguard she says something like, “It’s not too different from being a mercenary.” Except.... he didn’t say a word about being a mercenary. She realizes she’s slipped up and goes, “uh... I guessed! From the sword!” There’s another moment where Cloud tells her to stop acting like she knows him but.... my theory is: she DOES know him!!
There’s other hints too. Lots of them.
Edit: my only thing is—I don’t think she’s there to get a happy ending. I think she’s fully prepared to die again." --
Ribunn
"I feel her looking for a second chance at happiness would be inconsistent with the part where she says Cloud can't fall in love with her. Too much uncertainty at this stage to be sure I guess, but interesting theory nonetheless.
Also LOL at Time Janitors" --
Calaroth
"I actually do believe Aerith is from the future and she’s Sephiroth’s foil. I don’t believe she is doing this for a second chance. There’s a scene, when after they fall into the sewers, Tifa says she can’t believe they would ever really drop the plate but if it will happen they need to stop them. Aerith hesitates, as if she knows they cannot stop that from happening because things need to play out as they should in order for Sephiroth to lose this battle. Tifa immediately picks up on the fact that Aerith is hiding something and says, 'Aerith... what aren’t you telling me?'" --
Ribunn