Shelley, has your mother been tested for hypothyroidism? That might account for her iron deficiency anemia. And, if she's hypothyroid, treating that condition might resolve her anemia without the need for iron supplementation. Here are a couple of links which talk about hypoT and anemia:

Iron and hypothyroidism - Stop The Thyroid Madness

Linking Thyroid Problems, Anemia, Fatigue, and Loss of Cognitive Ability | Health & Wellness News

As we get older our thyroid function gradually slows down. If she has been tested but only with the TSH test, please be aware that TSH is a pituitary hormone (not a thyroid hormone) and it doesn't show the whole picture. A more complete thyroid panel might reveal something.

I hope she does well.