Have High Diastolic Bp. Have Been On Medication And All Test Done. What Can Be The Cause?

My wife's systolic bp is around 125-130, which has come down from the highs of 150 about six months back. However, the diastolic bp is still pretty much in the same range of 95-100. We have consulted many physicians, duly taken suggested medications, and drastically changed the eating habits to minimize salt intake and increase fruits and vegetables. We've had all the test done and the reports were largely normal. Could you please help me as to what is the reason of diastolic being so firmly in that rather high range and possible solutions.