I would like to focus on one part of Doctor Simsek's answer - "We should also consider the questions: Are there any signs of hypoxia? How are the vital functions during daily physical activity?"
If your grandmother has been living with a hemoglobin of 8 her body has learned to deliver oxygen more 'efficiently'. Notice this comment from an article authored by Dr. P Van der Linden of Belgium. I have taken the liberty of underlining key phrases.
"ACUTE NORMOVOLEMIC ANEMIA:PHYSIOLOGICAL AND PRACTICAL CONCERNS (Abstract): The adequacy of a hemoglobin concentration in a given clinical situation depends on whether a sufficient amount of oxygen is carried to the tissues to meet metabolic requirements. Therefore, the decision to transfuse a given patient cannot be based only on the hemoglobin level. Rather, rigid adherence to an arbitrarily predefined transfusion threshold will result in the over-transfusion of some patients, but also in the under-transfusion of
others. A better knowledge of the physiologic responses developed during acute isovolemic anemia and the clinical factors that can limit the ability of the organism to maintain adequate tissue oxygenation in these situations, will allow the clinician to better define the transfusion trigger for each patient."
Notice the article recommends NOT to transfuse due to some number i.e. hemoglobin count. He recommends treatment guided by how well the patient is doing.
This article is discussing Acute Anemia (very serious), your grandmother has Chronic Anemia (long term) but the issue of whether she can live well enough with a lower than normal hemoglobin is the same. In your grandmothers case physicians would want to do as Doctor Simsek says. Assess how well she is doing physiologiclly (how well her body is functioning) and determine treatment and where to place her at discharge based on the whole picture.
A comment based on research and personal experience: The fall in your grandmother’s hemoglobin is very likely hospital caused. When she was admitted did they begin taking blood for testing and infusing water? If your grandmother is a small person and if she is frail it doesn't take too many days and her hemoglobin will fall. Take away the cause (hospital) and her blood counts should come back up, especially if they continue treating her with EPO and nutritional support.