I'm curious to know why you are posting and not your wife since it is her with a condition not you?
When in doubt it never hurts to get a second opinion, especially when a doctor dispenses pills rather than advice. Your wife's "fbs" [I'm assuming fasting blood sugar] indicates prediabetes. This can be corrected with proper diabetes nutrition, maintaining proper weight and daily physical exercise.
Does "pp" stand for postprandial? Without knowing when, or how the 256 mg/dl test results came about your wife should ask the next doctor, preferably an Endocrinologist - a diabetes specialist - for
1. A1c test [HgBA1c, HbA1c] - gives a more reasonable view of the glucose [blood sugar] over the past 3 months. Normal is <5%.
2. Pancreas Insulin test
3. Thyroid TSH test - a malfunctioning thyroid may disrupt pancreas insulin production
These tests will help the doctor determine why her postprandial levels are so high.
I'm not sure what your question is.
During the course of an examination a physician normally explores many aspects of a patient's life, to include recommendations on diet, exercise and medication.
I am sure there will be additional testing after your wife has been on this medication for a while.
The prescription is reasonable, relatively safe, and, other things being equal, there seems no reason to simply change doctors.