I would recommend a high-carb/low-fat/low-sodium diet such as 80-10-10, Starch Solution, or Engine 2 diet. I eat a combination of them called Raw Till 4 program, lots of raw fruit morning through afternoon, then starch-based cooked meals in the evening.
I'm pretty sure high-sodium is contributing to her HBP and high-fat is actually the real culprit in diabetes, not sugar. Watch this diabetes video that explains why:
Just make sure she eats enough on those above diets because since they are low-fat, they are easier to accidentally under-eat on because you have to eat a larger volume to make up the calorie difference.