My gf has a job where she works with clients in appointments at their houses. Often she goes over her hours. Apparently her boss has been adjusting her timesheets and paying her only for 40 hours per week. He didn't talk to her and tell her not to go over the hours, he just didn't pay her for them. When she confronted him, he said it was because the job specified she is only to work 40 hours per week, so she would not get paid for the extra hours. Even when she had no choice but to work OT. Is this legal?