suddenly bad gas mileage

Poor fuel mileage issues can be difficult to diagnose but I can say for sure that the hoses, struts, or leaking oil pan would not cause a drop in fuel mileage. The engine control computer will make adjustments to the amount of fuel supplied to the engine based on feed back from the oxygen sensor. I would suggest a complete diagnoses of the fuel system including possible fuel leakage and monitoring the computer "fuel trim". If no problems are found replacing the oxygen sensor may help but there is no way to know for sure.

Oxygen sensors are worn out, filters, plug and wires need to be replaced. Clean the MAF as well. All will make a difference. The struts were shot at 50-60K, hoses at 75-80K mark. If your keeping the car then replace all the worn items. She'll feel like a new car but a 1/4 the price.