The truth isn't always the worst thing, IMHO. Willing to truly let go of her to hold onto yourself is being a grown, independent, noble man. By this, I DO NOT mean that holding onto yourself=pride or withholding love to save face. I DO mean that holding onto yourself is staying true to the fact that you will not accept living in a marriage in which your spouse is miserable because of you. Good, I say.
She could possibly have taken your response as you don't care enough, you're "letting" her slip away, or you truly aren't convinced that you are her man. I don't see why you couldn't briefly explain what you just wrote here (the part about you truly not wanting to live with a miserable spouse) in a loving way, just to be sure that she is clear that you are still "all in" this marriage.
If you think it should/could be said, you can still something to the effect of what DQ suggests (one more REAL try). Again, IMHO (and I MEAN *humble*).
