I'm so sorry. That looks pretty bad, honestly. As
@casportpony said, it wasn't your fault, nor the fault of assisting. I think the malposition caused her to break the shell too soon. And maybe the zipping action was her actually trying to get into proper position, and more of an accidental pip/zip.
But there is still a chance of survival! So don't give up yet.
I don't think I would try putting anything on the sac. The inside of the sac is liquid, so it can still absorb quite a lot of it. As it gets smaller, think like a balloon deflating slowly..... the outer casing may be hard, but it will also shrink.. If enough gets absorbed for survival, you will eventually be able to remove the part that gets hard. It will kinda end up like a scab. But I'd rather it be a little hard, than too soft. Less risky of rupturing, in my opinion.