She may be earning a bigger paycheck as a manager but she's not hourly and probably dislikes working "overtime" due to lack of "overtime" pay. When I worked in the hotel industry my pay as a department head was based on working 45 hours a week. I never had trouble getting any of my staff to come in and work over though, they all loved getting overtime, especially when a call in meant that they got 4 hours pay for it.