He will have taken note of her overall health and how the anaemia is effecting her day to day quality of life in making a decision. In this case, it appears that the GP has made the decision that the Hb level, although low, seems to be reasonably well tolerated, and that therefore the reason for the chronic anaemia be investigated prior to starting treatment.
Although iron deficiency is the most commonly encountered cause of anaemia, there are different reasons for why that anaemia is occuring that might well affect the treatment. Indeed there could well be reasons other than iron deficiency for why your friend has anaemia that would render iron replacement therapy unnecessary and ineffectual....