I saw a British documentary where a diabetic husband and wife had festering open wounds on their feet that would not heal. So disease-free, lab raised maggots were used to eat the dead flesh. They won't eat living flesh. It looked gross but it worked. The older maggots were exchanged a few times with younger ones and the couple's feet healed.
Even if I am a medical doctor and I didn't trust to the natural cures, now I saw with my own eyes that's possible! Couldn't believe it! My friend told me: JUST TRUST ME, This leg is already compromised, wouldn't be worst then that!
That's so wonderful for your granny! Good to hear.