I would say courteous because since Anna is rude, Bess is the opposite of that trait. Courteous can also mean that Bess is respectful to her employers and would rather meet her deadlines and come right on time to work instead of doing what Anna does.
I can see why you would choose dependable. It would have worked out perfectly if the line 'but Anna is rude to customers' wasn't included. Since it is included, courteous should be the best answer that makes sense on all territories.
