You gotta ask your doctor what KIND of anemia your wife has, and your doctor should be answering these questions for you. If you're not getting answers, get a new doctor.
As laFiera said, there are many kinds of anemia, the end result of all of them is that the body has decreased hemoglobin, thus decreased oxygen carrying capacity to the body's tissues.
Some causes of anemia are rather simple to correct, such as with the iron pills. If the cause of the anemia is genetic, though, no amount of nutrition will cure the problem.
Sounds to me like your doctor did a lousy job of informing you. NEVER leave the doctor's office until ALL of your questions are answered.