Increasing Blood Sugar. Sugar levels.

I have a sister who's carrying and now it's her 7th month of pregnancy. In recent check up, we have found out that her blood sugar level is increasing for which the consulting gynecologist has prescribed diabetes tablets glyciphage sr 500, one in the morning and one at night. She also advised to check the blood sugar value 4 times a day. While checking today, her blood sugar level was found to be higher after 2 hours of having food. The highest was 166 mg/dL. Since the time when sugar level was found high, she is not eating any kind of sugar rich foods , not even fruits. She used to eat a banana and few dates in the evening which is part of her prescribed diet by the gynecologist. We ate all having difficult times and cannot tolerate this tension until her next check up. Could you please advise me with your thoughts of what's going wrong with her and kindly advise us about the food/fruits that she can have during this time which would not affect her blood sugar levels. Thank you.