Diabetes problem. Have suggestions!

My mother is a diabetic for nearly last 7-8 years. She is also a patient of thyroid. She is under treatment of a physician (not a diabetes specialist) for last few years. However for last 4-5 months she is constantly having a high sugar level i.e. around 300 after taking meal and nearly 240 before meal. She is also taking regular doses of the prescribed medicines and also abstaining from sweets and other prohibited food items except taking once in a while. For last 4-5 months we r having a weekly test of sugar level and finding the figures every time on the higher side. The higher level shows its effects and she every now and then has some or other problems, sometimes very serious. We are unable to understand the reason or finding any way. Can we please have suggestions regarding treatment, life style to follow, fruits/vegetables/eatables to take or avoid. Pls. Share the names of the endocrinologist also. Thanks