Maybe this'll interest someone. Swedish radio just released a documentary about Britney with Alex Kronlund as an interviewee. He plays a Cheiron-era demo that was meant for her but was a little to personal or controversial for release. It's called "Britney's Gonna Snap".
Not sure if it's available internationally.
https://sverigesradio.se/p3musikdokumentar
55:10
Tack!
It is, it's available.
Her voice is unrecognisable.
Maybe should have mentioned that he used a demo vocalist, so not Britney :)