I did tell her about the audio recorder after we started piecing. Up until that point, she had no idea how I discovered anything. The way that I found out that the A was still going on during our S was while trying to install drivers for a new printer onto my daughters laptop. The laptop used to belong to my W. When I went to install the drivers, I saw that the computer still had an account for my W on it. I logged in to that account and was able to read her emails and her FB login credentials had been saved to the account. I was able to read all the FB Messenger messages that they had been sending to each other during our S. That gave all the proof I needed that it was in fact still very much ongoing.
Me: 48 y/o W: 47 y/o Together: > 20 yrs BD: Dec '15, then S 2nd BD: Mar '16, then I filed for D April '16: started piecing