Blood glucose of 500 mg/dl is an emergency/semi-emergency and should be handled accordingly. She needs urgent attention and should be treated with Insulin if she is on oral drugs. Risks are enormous like kidney failure, blindness and nerve damage leading to diabetic foot. These complications come under the heading of microvascular complications. Other group called as macrovascular complications include heart attack, brain attack and peripheral vascular disease.
Please take it seriously and get her treated from a diabetologist / endocrinologist or a good physician. She needs a detailed work up.