I can't say if I could ever trust her again and whether I would be living in constant fear that at any point the ILYBINILWY could happen again?
Then why would you even consider giving it another try? Just b/c she would want it? Just like when she decides on a spur she wants to go back to school, and for you to accommodate her......and your very first thoughts were that you probably should.....but you'd ask to make sure. Good thing you did!
You LBNG's (left behind nice guys) are way overtrained to accommodate your WW, and whether you can see it or not......it really is obvious to one who is not a LB or NG.
BTW, on the trust issue, that's why the burden is on the shoulders of the wayward spouse to earn back your trust by proving, over time, they can be trusted again. It is not up to the betrayed spouse to have no choice but to trust the wayward. No-no, don't buy that wayward b.s. for a second. If the wayward doesn't want to do what it takes to earn the trust, then send them on their way. They aren't worth it.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!