I to am familar with old lady drivers. My grandmother only drives once or twice a week usually short trips of less than 5 or ten miles sometime less than 2 miles. That is why when she gave me her 88 Bronco II it only had 43k on it.(She has now replaced it with a 05' Honda CRV which has a whopping 2,000 miles on it currently)I'm currently running an arx treatment through the engine do to her short trips and 3000 miles conventional oil change interval, she only drove 2 to 3k a year so only had oil changes once a year. If the car is inherited to you just do an arx. In the meantime have her use a good oil and add some LC and FP.