AK Guy - Your wife will start feeling dramatically better once this is fixed.
BUT - if the doctors don't know WHY she isn't absorbing iron and B12 - I suggest you consider celiac disease or gluten sensitivity. (A common problem where an autoimmune reaction to gluten in wheat and other grains, causes inflammation of the small bowel, resulting in poor absorption, especially of B12 and iron!). The treatment is simply to eat a gluten-free diet - no wheat, rye, spelt, barley.
Her doctors may have already tested her for celiac disease - but I caution you, even if the test was negative, she still might be gluten sensitive and benefit from a gluten-free diet.
An excellent book on B12 deficiency is called Could It Be B12? I highly recommend you both read it - once you do, you'll know more than most doctors do about B12 deficiency. (I'm a doctor, I know).
