If the woman waits until Monday morning to return the car, she will be out of pocket another day's rental. If she returns it early, she faces the problem of possibly not being able to use the car for the purpose for which rented it in the first place.
Incorrect - Enterprise has dealt with this by having their "weekend rates". There is no charge for Sunday.
i.e. if 3 days is usually $40/day, a weekend rate for Enterprise is $20/day (50% off) to cover the closed hours. There is no difference in cost between a Saturday at 12:01pm drop off or a Monday at 7:30am drop off.