So she has been aware that she is not being the sexy wife that you want. She has taken a lot of effort to work herself up to the point where she can put the sexy clothing on and expects you to be overcome with desire and ravish her on the spot. As time went on and that did not happen she lost confidence and went back to her usual mind place.
The other problem regarding this kind of thing is that for many of us, work is stressful and we need time to get our heads in the right place before we can consider getting down and dirty. She is so wound up thinking of what she is doing and not considering how you might be feeling.
If your wife is struggling to find the confidence to do this on her own, try finding the right time and remind her of how she dressed up for you. Tell her you are going for a walk and you want to find the same woman when you get back. You might also tell her that failure on her part may require a spanking but that will depend on your relationship with your wife. For some people taking away the need to think in this way for themselves is a form of release. This is why being submissive is so popular.