Diabetic now requires insulin. Mom now?

Hi, My mother is diagnosed with diabetes abt 3 years ago. She also has Thyroid problem from more than 10 years. She is an Arthritis patient from abt more than 6 years. Until last 6 months the sugar level was in control with medications. Now she started complaining abt giddiness and we checked sugar levels shooting up. Dr. prescribed pills of more power twice but still sugar levels are high, now abt 350 post lunch. We consulted new doc today and he says, she needs to be on insulin from today. Will insulin needed for few days and lifelong from now on.? R there any chances that without insulin, sugar can be controlled to my mom now? She can't walk more due to joint pains. Only option for lifestyle changes is control Diet. Request to let me know if u have any suggestions Thanks