Hello & Welcome to Just Answer,
Having gone through your description, two things are evident and these are:
(a) The diabetes is not controlled (urine may show presence of sugar if the blood sugar levels are over 180 mg/dl). Since traces of protein have not been found in the urine, it seems that her kidneys are functioning OK, and that there were no ketones in the urine sample.
(b) Although a low blood pressure is said to be below 90/60, she needs to keep herself well hydrated (drink plenty of unsweetened fluids/ water and needs to get her blood pressure reviewed as well).
Having said that, your sister would require a blood test for measuring the sugar levels, in the fasting as well as after meals (post prandial). I feel that her doctors would also like to check her Hemoglobin A1C test which will show the average sugar levels for the past two or three months, and adjust the anti-diabetic medicines accordingly.
I hope that this information helps answer your query. Please feel free to inquire if you have any remaining concerns/ doubts, as it shall be a privilege and a pleasure to try and help as much as I can. Best wishes.