GH, hugs to you for a hard weekend. I react the same to the "shutting down" mode, b/c H does the same. I panic b/c to me it means "he's running away and to someone else" and being in the dark about someone's feelings is hard. Every so often we have a really candid conversation, but it takes H a while, since I used to react so poorly....safety is a big issue for him. But the fact he opens up is a big risk. Same with your W. What she told you was a big risk. For some reason she's in the habit of taking that small risk, but not following through with the actual conversation of what she really wants to say. In ways, you do the same. So there can be no real opening up. Of course, this takes time, and you 2 don't fully trust each other yet.
I agree with OT. Open up a little. You're both not doing that for fear of something. Your fear is rejection, a bomb. Totally understandable. But, you won't get that open R if you don't do the same. Like in DB, what you're doing now was fine to get you out of the stage you were in, but it's stagnant now. What can you do differently to push you out of the "fine" plateu? Think....be creative.
Think of why W has a problem opening up? Fear of facing the truth? Fear of things falling apart? Fear of guilt? If so, then try to be creative in making her feel safe. Be candid and open in stating what you think her fear may be, understandingly, and make her feel safe.
Another thing, I learned myself and hopefully it's valid....don't bring up OM right now. She can't even open up to talk about what's on her mind, she's certainly NOT going to broach that ugly subject, esp. if you tell her that it bothers you and hurts. She can't get a hold of opening up, let alone coping with your reactions. First work on opening both of you up to small, candid talk of R. Safe and trusting. Even if they're rare, if they're good, they make a HUGE difference and will really help her anxiety attacks.
OK, I don't know everything, just my 2 cents here....hope it helps.