Theran.
It is as clear as it could be as it reflects on Aerith's eyes. Most of her memory was contained on the planet; but very soon, the planet will just become a part of her memory.
"It's time to say goodbye."
"I said goodbye a long time ago."
The planet also reflected in Diana's eyes, but barely. For her, the planet has just always been a memory of her greatest failure—a reminder that her efforts weren't enough.
"Why would you say goodbye to a planet?"
As for the Princess of Varoif, her eyes were completely elsewhere; not reflecting even a single color of Theran as she just looked beyond the expanse of space.
"I don't know about you people, but I only have bad memories of the place."
Xra was also there, floating in the expanse of space—her eyes weren't even on Theran in the first place, she was just here to make sure that Diana doesn't escape before trying to resurrect her husband.
