We can reasonably guess that she's sincere based on NWS and what she considers her greatest sin. There might be a backstab involved, but right now we could use a temporary ally, as the Greater Akuma is still a great threat. And, if nothing else, if she sees our full-out combat prowess, I don't think she'll be that eager to betray us.
Right now, we have two basic options:
1) Fight her
2) Not fight her
I am for not fighting her.
She's sincere in her desire to keep her powers and escape her slavery. That doesn't make her trustworthy, except in the sense that we can be reasonably sure she'll prioritize that over anything else.
If she's willing to play the game she's trying right now I wouldn't bet on her being particularly gutless in practice either.
She wasn't willing to let go, but she's still acting on a desire to spiritually manipulate her demon lord boss.
This does come down to fighting her or or fighting her, but the context around that changes which option is preferable.
A really good trick and something set up that allows this to be a long term -as in as essence level or two from now at least- operation would incline me towards helping her.
If she had degrees of support we could provide, and wasn't banking on us carrying the effort with exalted powers I'd also be more inclined to try negotiating something.
On the other hand if she can't articulate a clear approach of some kind, it relies on us doing everything, or puts us in a position where she could do something like sell us out to Emma-O in exchange for ownership of her soul and a severance package including all her current powers then I'd rather bite the bullet now.
[x] Yog
We are exalted, trying to take on impossible things is our norm, succeeding at it is par for the course given time, let's try and redeem Emma-O, and as such not fight the one who wants it.
Edit:
Well, this plan is working on that too it seems, so:
[x] BronzeTongue
To be clear, I'm only working in that direction in terms of seeing what her idea is.
Exalts do impossible stuff all the time, but they do have limits and some ideas are just stupid even for them. I don't want to sign on to something without hearing the whole arrangement laid out first.