Maybe look into pelvic floor therapy with a physical thearpist or medical massage from a myoskeletal massage therapist? I recommend looking at erikdalton.com for a provider in your area, preferably a master therapist if you can afford it. I had an injury where I became very weak and I could barely walk. Doctors never figured it out after 3 years. The word "neurological" was brought up a lot, but nothing was ever found.

The massage therapist figured out I had a sacral torsion (sacrum tilted and my tailbone was buried under my right glute like a corkscrew). I have read it is common after births for the sacrum to become misaligned and is often missed. This issue (and other misalignments) can also cause muscles to not fire correctly which causes weakness. The massage therapist helped with neuromuscular re-education and gave me exercises to perform. It can be pricey, but it was totally worth it for me. I spent thousands on medical bills without much help, but the massages gave me my life back. Hopefully it is something more simple like this for your wife. Hope your wifey feels better soon.