Please suggest some useful foods for diabetes

Ask her to soak methi overnight and have it early morning in the empty stomach. Bitter gourd juice and Bottle gourd juice are good.

Oats, Garlic, jowar are good for Diabetes. Rice, Maida, sweets bad for diabetes.

barley-1/2-1 cup a day,cinnamon or dalchini-1/2-1 tsp/day,onion-1/2 cup /day,raw garlic -3 cloves/day n lemon 1/day..helps 2 maintain sugar levels

she can eat 5-6 small meals a day , instead of eating just 2/ 3 big meals in a day .. this will raise her sugar levels slowly ..

avoid fruit juices of all sorts , instead a whole fruit can be eaten in between two meals (not with the meals) .avoid fruits like banana, mango, grapes, custard apple, and chikku these are high in starch.
increasing her fiber content will also help , simple tips like using whole wheat flour , whole wheat bread instead of only maida bread , and salads 15 min before her meals will help her .

along with the diet you also need to check on her activity levels, a 15 min walk after every meal, will help her in keeping her pp sugar level in control , and if her fasting sugar levels are high, thn a late eve walk of around 20 min will be helpful.