Oh my god, Anon, I am so sorry. Reading your secret I was seriously going "are you me?" because I went through a couple years of my life doing a big project with a destructive co-author; I really really know how you feel and it fucking sucks. I finally got to a place where I cared more about my own mental health than about keeping the story together and maintaining my friendship with her and managed to get the fuck out, but it was really hard. I hope you have the strength to stick with it without going crazy, whichever road you decide to take. Just know that my heart goes out to you and that I hope you make the decision that is best for you and pull through to the end. ♥