[Shadow5YA]

Originally Posted by Kanon

Spoiler for Ending:

How do you explain Nanaki was able to sense Aerith in the last cutscene? She's definitely a lifestream ghost. She doesn't confront Cloud about her death for the same reason Tifa never confronted him about his inconsistent memories: too afraid his mental state is going to deteriorate even more. Of course, this is just delaying the inevitable. And the reason she's okay with him chasing after Sephiroth is because there's nothing she can do about Sephiroth anymore now that she's dead.

I'll make a prediction: Cloud will be a boss battle in the third game after Sephiroth mindbreaks him.

Spoiler:

The Nanaki comparison only makes Cloud look even worse.

Keep in mind that Nanaki has also been experimented on by Hojo, and that despite that, he still could not see her.
"Sensing" her is also questionable if you pay attention to his body language. He raises his head, but doesn't turn toward where Aerith is supposed to be.

There's also multiple occasions where Aerith disappears when Cloud isn't paying attention.
You can see here that when Cloud is looking in Nanaki's direction, Aerith is there:


But then when he's looking at the colorless materia in his hand, Aerith is gone:



If she were a ghost, she would be there regardless whether Cloud is paying attention or not.