It's the MLC, not the infidelity

[SirPrizeMe]

I just can't believe she wants out. She is messed up in the head right now and doesn't know what she wants, but a dissolved marriage isn't really it.

I totally get this sentiment. In my case, I acted a little too much on it. It is one thing to think this way, it is quite another to act upon it. I was convinced that "divorcing doesn't make any sense for us", and my actions along those lines, were viewed as controlling acts. By working directly on the marriage (ie, not DB principles, not validating enough, not detaching, trying to stick to MY timeline), I was driving her away.

I text something back (probably shouldn't have, correct?

Hard to say. It's up to you. There's no pat answer. you have to decide these things yourself, applying the principles. Sometimes the prescription is to stand back, put some distance between you. Sometimes the prescription is to engage more closely and be more responsive. I'm trying to NOT be as available and solicitous in my relationship, because that is a true 180 for me. I've always been an acts-of-service person - someone who shows love with acts of service (reference the 5 Love Languages book). So, by being less responsive and solicitous, that's a 180 for me. your situation is different.

...and mention that my therapist wanted to make sure I told her hello from him

It sounds like a nice, friendly gesture by the therapist. it also sounds like it was received as a provocation by her. This is one of those things. Live and learn. Next time you maybe have something to think about regarding the relationship between your therapist and your wife. I don't have a pat answer here, either, but it seems like something you need to think about.

(My therapist is a great guy who knows us both and thinks we can repair our marriage in time).

just a side question - have you told your therapist about DR book and the DB philosophy? You might wish to engage your T as an ally in your efforts, if you haven't already.