How can diabetes and hypothyroidism be managed together?

My 56 years old mother is diabetic for the last 30 years. She is taking insulin along with Glycomet 850 twice daily. Insulin dosage: (taken for the last 2 years) - Levemir Flexpen: 10 points (at night) and Novorapid Flexpen: 10 points (in morning). Recently, she was complaining about occasional numbness around her face and palpitations in the morning. We did a T3, T4 and TSH tests and found that the TSH level was about 12.6 mg/dl. LFT and ECG were also done recently and they appeared to be normal except for the SGGT appearing to be 55.0 u/i. The doctor advised her to take Thyronorm 50 mcg empty stomach daily. But after taking this medication for about 5 days, things have deteriorated. Her appetite has decreased and at times she develops a vomiting tendency. We have checked her blood sugar levels and the fasting count appears to be 159 mg/dl for the last 2 days. The dosage and power of Thyronorm, which was prescribed by the doctor was not suiting her. Please advise.