This patient's most likely diagnosis is β-thalassemia intermedia. She has erythrocyte parameters typical for thalassemia (hemolytic anemia, microcytosis, target cells), a common genetic disorder caused by a mutation in one or more α-globin or β-globin genes leading to a quantitative deficiency in the synthesis of that globin chain. The imbalance in globin-chain synthesis leads to impaired production of hemoglobin and ineffective erythropoiesis, with intramedullary hemolysis and often chronic anemia. α-Thalassemia and β-thalassemia are usually differentiated by hemoglobin electrophoresis, with β-thalassemia associated with a slightly increased hemoglobin A₂ and some residual hemoglobin F. Because of this patient's increased hemoglobin A₂ level, she most likely has β-thalassemia. Because of the low-level hemolysis associated with either type of thalassemia, patients with thalassemia (and other chronic hemolytic anemias) can commonly have low folate levels if dietary intake is inadequate, leading to worsening of chronic anemia.

Although most patients with β-thalassemia intermedia are anemic at baseline, most are physiologically adjusted to a hemoglobin level between 7 and 10 g/dL (70-100 g/L). This is not an anemia associated with chronic inflammation.

The patient's iron studies do not indicate iron deficiency; in fact, her ferritin level is elevated, which is often seen in thalassemia. Therefore, she is unlikely to be experiencing iron malabsorption.