Final answer:
The nurse should advise having a professional medical evaluation to assess the mother's symptoms of forgetfulness and disorientation, as they might indicate Alzheimer's disease or other forms of dementia and should not be ignored as normal aging.
Step-by-step explanation:
The nurse's best response to a friend concerned about his mother showing signs of forgetfulness and disorientation, as well as difficulties in daily tasks, would be A) "Have you taken her for a checkup?" This question encourages seeking a professional medical opinion to properly assess the situation, as such symptoms may indicate the possibility of Alzheimer's disease or other forms of dementia, rather than being merely dismissed as normal aspects of aging.
A checkup would involve a physical exam, lab tests, detailed interviews regarding memory and mood changes, cognitive assessments, and possibly brain imaging, to accurately diagnose the condition and determine its severity. Given the additional information about her trouble with paying bills, memory gaps, irritability, and disorientation, these could be warning signs that require medical attention and are not just stereotypes of aging.