The best interpretation of the employee's statement about the mean number of hours she works per week being 42.5 is:
D. If she spreads the hours she works in a year evenly over all the weeks she works the result would be 42.5 hours per week.
This interpretation accurately reflects the concept of the mean, which is the total number of hours worked divided by the total number of weeks worked, indicating an average amount of time worked per week.