Talk to General Physician on Sugar Level

My mother is pre diabetic patient. She is using glucophage 500 twice a day. When she checks her sugar level at fasting, its around 150, but in non fasting check, its around 100-120. Aren't these figures a bit messed up as fasting levels should be less and regular levels should be high Need guidance in this regard.

Moreover, is there any permenant solution of diebatic or she has to carry out the particatice of taking these medicines all her life?