Take this with a huge grain of salt given the source- Dave Cullen, but it is based, in part, on this article about Val Schnurr. https://www.washingtonpost.com/wp-srv/WPcap/1999-10/14/026r-101499-idx.html
so I'm assuming there may be other articles out there that fill out the rest of the picture.
In his book he writes that Misty Bernall was contracted to start writing the book about Cassie in late May. In June, Kate Battan informed Misty of what really happened, even playing the 911 tape of when Cassie was shot. Battan apparently encouraged Misty to continue with the book, minus the She Said Yes stuff. But since that was the entire public appeal of the book, Misty spoke with her publisher. She and the publisher visited with the three witnesses (whom he doesn't name) who said it was Cassie who professed her faith and decided that their word was good enough and they'd continue the book, with the martyr bit still in there.
Cullen also wrote that the Bernall's (and their publisher) had dinner, on separate occasions, with the Wyant's (and Emily), and the Schnurr's (with Val). Emily was scared of hurting them and of repercussions so was a bit vague when asked if she'd heard the exchange between Eric and Cassie; the Bernall's seemed to feel she wasn't saying it didn't happen, just that she didn't hear it or didn't remember it. Val, however, was clear in explaining what happened to her. The Schnurr's asked the publisher to slow down on the release of the book until all of the evidence was out, but they refused to do so.
After the book was released in September 1999, The Rocky, came out with a story debunking the myth and Emily Wyant allowed her story to be used. The publisher went after Emily, trying to discredit her. At that point, it seems, the Bernall's realized the truth.
As far as the Rachel said yes stuff, I also feel like that came out years after the Cassie debacle.