There are many causes for itching in elderly people. If her blood investigations are all fine, that's a good thing. The cause may be due to senile pruritus, excessive dryness, uncontrolled blood sugars, thyroid abnormalities or drug (medicine) induced. These factors need to be checked before prescribing treatment. As of now, you can use Tab hydroxyzine 25 mg twice daily and a good medicated moisturizer twice or thrice daily. Other practices which may help, include taking bath with lukewarm water, and applying moisturizer just after bath. Keep the skin hydrated and moisturized as much as possible. You can consult online, for better assessment.

Don't worry...you are suffering from allergic dermatitis causing this itching sensation... Specific medicine available for good control... Treatment depends on the severity..Do direct online consultation for detailed prescription by sending photos.

I would advise her to use less soap application and use coconut oil at night all over the body. Most common cause of itching in elderly is senile xerosis that is dry skin due to old age.