Hello sir I am sure you wish the best for your grand mother, but in old age two things are important one is strength to walk second is will to walk she can move her extremities means no physical handicap is present diabetes makes muscle sore and weak so though she can move her limbs to bear weight on them is different. What you can ask your doctor is about her bone mineral density she may be having osteoporosis and also you may need to rehabilitate her by making her ambulatory with help of an walker , ask your physical therapist regarding it. And lot of emotional support is needed from family side to inculcating the will in her to walk rest if u have any questions feel free to ask thanking you