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Hello and thank you for your question.
Based on your description your wife most likely has neuropathy. This is a condition where the damage to the nerves can give burning pain in hands and feet and which can progress and radiate to the knees and arms.
As she has history of smoking she would be at higher risk of developing neuropathy.
She needs to see a neurologist who can order EMG nerve conduction test to evaluate the damage done to the nerves.
Medication like lyrica can help with the pain. She also need to stop smoking to prevent further damage.
Please get back to me if you have any further questions. Thank you.