Hmmm... Notice that apparently you aren't willing to be totally honest with her either...
Anyway, feel free to ignore this post, lol. No doubt a lot of this is projection about things that went on between me and my X. But I really think there are a lot of the same dynamics between you and W...
IMPO, what she needs is passion, sex, strength, honesty, confidence, and self-respect from you.
With respect to the self-respect, I'm not sure why you should be willing to live with reminders of OM all over the place. Why don't you share your fear with her and see what she says? If the panties do relate to OM, tell her they hurt you and ask her to get rid of them and then take her to VS for something other than pajamas and warm ups.
With respect to passion and sex, maybe she was waiting for both all weekend and never got either and that is why she is starting to feel frustrated and hopeless. A sexless marriage isn't any better for her than it is for you, maybe worse as she was the first one to seek fire elsewhere. My guess is that she is, or will be, starting to mourn the loss of her identity as a sexual being that inspires and feels passion because she doesn't see a place for that person in your M and nothing is changing to make a place. A woman who is content living an asexual lifestyle doesn't wear sexy underwear like that to begin with...
Now, I believe she told you that she wasn't ready for that in Ireland because she was still involved with OM. What makes you think she still isn't ready?
How much of this "sex being off the table" thing is really all about you, your own anger, resentment, and insecurities? How much is due to you needing honesty about the A to move forward? If that is a big part of it, why not let her know that a great sex life is important to you and that right now your own need for more openness and honesty about the affair is a barrier to that?
BTW, I'm not sure if I can explain this, but you seem to implicitly support the idea that a married woman is not a hot, sexy, horny woman that craves sex. Why do I say this? One example is your 5LL talk in which you quickly say that it isn't all about sex for you in a way that sounds to me as if what you are saying is, don't worry W, I'm not going to insist on too much sex because I know that would threaten and scare a good W like you.
I'm glad you are thinking about how and when to talk to her, it will be good for you to get clear about this in your own head so that if you wait, you know that you are choosing to live with the skeletons in the closet.
