I disagree with Scarred about validating only what is true. What we validate in DBing are feelings not facts. Feelings are never true or false, they are what they are.
That said, I agree with you. Validate what she feels. However, if you do not feel it, too, then you need not agree with it.
You can tell her you understand why she might feel that too much has happened to reconcile but that you do not share those feelings, or something like that. I think you were on the right path already.
In any event, you have decided to hold off on sending the letter. I agree, given your situation that waiting is for the best.
