No Promises to Keep being some bizarre, ill-placed love ballad written spur of the moment for Cloud alone was always narratively inconsistent in the extreme. We've said here for some time that it needed to be interpreted in light of her character as presented in the games. In Rebirth for instance, before the song Aerith openly admits to still being in love with Zack and after the song is shown to still be trying to shoehorn Cloud into the Zack shaped hole in her heart - right up until the end - before admitting he's just not a fit. Where's the narrative consistency here?
But now we know for definite. NPTK is a song not about any specific individuals, but all the individuals and her entire life and feelings and experiences. The 2 weeks she knew Cloud surely were special, but ultimately were flash in the pan compared to the rest of the 21 years of her existence. The people she knew, the family she had, the life of a Cetra. Everything in this song.
I guess what I'm saying here is, there's so much to Aerith. Trying to force every little thing she does to be validation of CA is an assassination on the character that has been intricately woven by the devs to be far, far more complex than just one exceedingly nuanced relationship. It's why I struggle with the chutzpah of Cleriths who continually accuse those who cannot get on board with the CA ship, through sheer inability to deny the story as presented, of "hating Aerith" - yet it is by virtue of forcing her into the role of Tifa, that of Cloud's own closest "personal connection", that the biggest hatred of Aerith, the real Aerith, shows itself in the fandom.
In any case, now the pieces can fit together. Aerith sings her song for, and about, everyone she cares for ahead of making the ultimate sacrifice. Remove that and what are you left with? Some awkward love confession that Cloud doesn't reciprocate? A confusing mishmash of signals given her growing realization of her fondness for Zack and Cloud's growing realization that Zack and Aerith are a thing? Just awkward, uncomfortable and overly dramatc. I'm glad we can listen to this song now and enjoy it as part of the beautiful story the developers have created for us.