it sounds like you're dividing 380 by 13 gallons, which is the maximum capacity of the tank. however, odds are she doesn't run it till it's bone dry every time. rather, she probably fills up when the gas light comes on, which would be when there's about 2.5 gallons left in the tank. so she's probably going about 380 miles on 10.5-11 gallons, which is over 35 mpg. which sounds about right for that car.