Shingles can be a real bugbear for an elderly person and it is common enough. It comes about through the nervous system and can be a reaction to stress or frustration or anger but it not all that helpful to tell the person this normally.
First aid treatment is to get hold of Hypericum (St Johns Wort) Oil and add a couple of drops of the Bach Flower essences Holly and Rescue Remedy. You will be able to get these from your health food store. The oil may be smoothed over the areas that give trouble two or three times daily sparingly and should quite quickly offer relief. The two Bach flower essences should also be added to drinking water as well. Just two drops of each to each glass of water during the day.
I have an internal mixture I can send to you to deal with the internal origins of the condition more effectively see: