I recommend your have a follow up visit with an ENT to investigate new advances in treatment of single-sided deafness. BAHA (Bone Anchored Hearing Aid) has increased popularity and many have experienced huge success from it. An ENT who specializes in BAHA can best determine if your wife is a good candidate for this type of treatment.
As far as the better ear, it's a good idea to visit an audiologist for an annual hearing test. Precautions for the better ear would be based upon the hearing loss history-- What caused the single-sided deafness?