The reason I asked if the car was purchased new is this - some new car buyers seriously abuse their cars because they know they'll be selling them after a given time interval. She may simply have inherited problems induced by abuse on the part of the original owner.
No, she’s the only owner of the vehicle, but her late husband apparently beat the Hell out of it. I maintain the car now, but parts aren’t cheap. I’ve replaced two O2 sensors, the spark plugs, the TPS in the throttle body, and do regular oil changes, but those parts alone were almost double what I paid for similar parts in my car.