Hi Dawny, sorry to hear about your Mum's stroke, hope she is recovering well. If she can cut out smoking completely, that will be the foremost best thing to help her future health. Does she take any medications for her diabetes? If she has been managing on diet alone, it might be time for her doctor to start prescribing meds. Having said that, a BG level of 170 (9.4) is by no means terribly high, especially if this is a random test, not a fasting one done on waking.
Your Mum would probably benefit from sticking to a lower carb diet, ie having more meat, fish, eggs, veg and salad, and much smaller portions of potatoes, rice, pasta, etc. She doesn't have to completely cut out all sweet foods (it would be miserable and impossible to stick to), but if she eats smaller portions and less frequently, she will be all the healthier for it. Fruit juices, smoothies and full-sugar soda drinks should all be avoided.
Presumably your Mum is under the care of a specialist stroke doctor? Is she taking meds for high blood pressure etc? Is she good about taking her medications regularly? Good luck with encouraging her to get her health back 🙂