What's kind of crazy I had just seen Ted Arfken's artwork for a Fallen Sister on Facebook so I've been lurking through the web trying to find some Chaos inspired Sisters of Battle. Came across this thread you guys had started. I found some sweet lore from Fandom, it looks like its a homebrew chapter. I'm new to the website I got it from so I don't specifically know who created it to give them credit for it. It's not mine but I found it a great read and if I ever did get into making a new army it would probably be something like this. I really find the Chaos inspired good guy armies pretty intriguing.
Ted Arfken's Fallen Sister
https://tarfken.artstation.com/projects/v2kDZd
Sisters of the Night chapter info
https://wh40khomebrew.fandom.com/wiki/Sisters_of_the_Night