Better post it here than tell it to her face. Trust me, I know. Posting here is part of your healing process. I do not just to get advice, but to get things off my chest. It's therapeutic.
As J said, your mind is going to wander - it's normal. It will subside over time. My W hasn't turned of read receipts on her msgs so I know exactly when she has read my message. Sometimes it was really late at night and I would wonder what the hell was she doing in between those hours. Now I don't even bat an eye. I don't even check to see if she's read it. These thoughts will slowly lose impact. I still think about all kinds of stuff, much less now, but it passes and it doesn't affect me - this comes with doing all the DB stuff like GAL, practicing detachment over time, and improving yourself.