I do think that you deserve priority in scheduling since you've been there so long. It isn't fair that you've had to work every Friday night for the last 2 years. Please find the courage to speak with your boss and ask her if your schedule can be modified so that you can have more time off to be with your family. You've paid your dues at this point, and you deserve to have more flexibility in your schedule than the part time girl who has only been there 3 months.