If she thinks metformin, especially alone, will help her with blood glucose levels this high, she is insane. Metformin is for mild type-2 diabetes. With those readings she is well into the insulin dependent part of the disease as I doubt her blood sugar, at any point, is anywhere near the acceptable value of ~152 mg/dL for type 2 diabetes. You could stack her on 3-4 hypoglycemic meds and I bet it wouldn't be enough. Without insulin she will never see an HbA1c of 7. Her only hope at this point is an inpatient stay to get her started on meds with continuous glucose monitoring to get it down without an unacceptable heightened risk of hypoglycemia. I would envision her on a basal, long acting insulin, with 1-2 hypoglycemics stacked to reach a reasonable baseline with a limited risk of transient hypoglycemia.