Hmm. Ive tried making chocolate from scratch and instant coffee too, but I think even I would draw the line at attempting to decaf coffee beans.
Im unsure as to the exact point of processing when the beans are ready for decaffeinating (shame on me), and although the various processes sound simple, I really dont think they are.
For example, washing beans in warm water for 8 hours with the water passing through activated charcoal to capture the caffeine molecules, then discarding that lot of beans but using the water to flavour charge the next batch seems like a lot of work, and would require lots of equipment. Then at the end of the process, youd need to know for sure how much caffeine youd managed to extract which means even more equipment.
Unless there are stated medical reasons, perhaps for variety, your wife may enjoy a blend of the mocha java with perhaps an SO? I would expect that 10-20% of an SO would make a fair bit of difference to taste.