I also would suggest having a glass of wine, or -- better -- an anti-anxiety pill right before meeting with her, if you got one.
Just go with no expectations, and LISTEN. If she says she wants a D, then I like what was suggested above by NewGal as a response.
Your wife (and you) will forever remember this moment. HANDLE IT WITH CLASS AND DIGNITY, and give her pause for thought. Tell her you love her, this is not what you want, but that you won't stop her if it's what SHE wants. Hold your head up high and tell her "you won't find anyone else like me, but I understand this is how you feel right now," or some such, so you DON'T SELL YOURSELF SHORT.
I would expect something from her that depicts HER as the suffering victim here.
