As long your mum is taking medications the way they should be taken and remains compliant, considering the fact that she is following her diet as well, non-reduction of sugar levels means the medications she is on at the moment is unable to get the sugars under control . One thing that need to be realized that the medication have ceiling effect on the effectiveness in terms of sugar level control. If they are not, as suggested by the sugar levels, they need to be changed or your mum has become insulin deficient and her insulin requirement is not meant by medications alone and there is a possibility that she would need insulin added to her regime as well. Please discuss with a specialist diabetologist who would suggest appropriate management regimen for your mum.

With these sugar reports her medicines surely need to be changed. U should consult a diabetologist along with her medicine details.