Your mother definitely has developed diabetes
. To diagnose diabetes we need to test fasting and post meal readings as you have done.
Fasting sugar >126mg/dl and Postmeal sugar >200mg/dl is diagnosed as diabetes.
It is essential to understand that most patients in diabetes do not have symptoms and so always there is a delay in seeking treatment. Uncontrolled sugar levels gradually then start causing damage to your kidneys, heart , eyes and nerves (EVEN WHEN YOU DO NOT HAVE SYMPTOMS).
In your mothers case, we do not know since when she has been diabetic. So it is essential that along with treatment you get her tested to see if the above discussed organs are still unaffected. Preventing complications is very important for a healthy life.
Coming to treatment you would need to get a diet plan
and an a regular exercise regimen. With changes in lifestyle we can bring down the sugars to some extent. Ofcourse she would need medicines, along with diet and exercise, weight control.
In diet cut off all sugar, sweets. avoid eating large meals and tell her to eat in small quantities every 4 hours.
A detailed dietary advise based on your regular type of food would be more helpful.
Hope this helps