I can see where a lot of the techniques may be more difficult in your situation, given your W's disordered thinking.
You got me thinking about the word "valid." In logic (the philosophy) to be valid means that an argument is sound - that it contains no fallacies and is provable. How can that ever apply to a feeling?
I guess we must extrapolate a bit. I think in the DB world what is meant by "valid" is really "acceptable" or "okay." As in, "W, I can understand how you might feel X and it is okay for you to feel X, there is nothing wrong with feeling X." The next step, if you do not feel X is to tell her "W, while I understand how you have come to feel X. I do not feel X."
I get that the problem for you lies in telling your W it is okay to feel X because, it may very well not be okay to feel X in your mind. But, the key is that she feels it in her mind. So, perhaps the trick is to appeal to her sense of logic. Ask her if she can see how, given the same set of facts, you might feel very differently about the same thing.
Not sure if that helps, or if it even makes sense. It has been a good twenty years since my last logic class, or any philosophy class for that matter, so I may be a bit rusty.
