My mother was diagnosed with diabetes last year with hba1c 8.4. she is taking glyciphase 1g daily. She has hba1c 5.6 for 6 months. Can she leave medic.?

Diabetes. There is no evidence that a hemoglobin A1c of 5.6 is superior to a 6.5. She can likely reduce her dose. It wuld be unlikely that she needs no medicine at all.
She should stay on. It sounds like your mother has type 2 diabetes and has had a very good response to Glucophage (same as metformin). Unless she has lost considerable weight in the past 6 months, her HbA1c will probably rise if she stops the metformin. She should discuss with her doctor before making any changes.