Your best friend is getting married next month, and you are the maid of honor

Your best friend is getting married next month, and you are the maid of honor. You have already purchased a nonrefundable airline ticket to attend the bridal shower. You work in a very small intensive care unit. You have been working 10- and 12-hour shifts and are near exhaustion. Your head nurse calls you two days before you are to leave for the shower and asks you to work the weekend. One of the staff has been involved in a serious car accident, and there is no one else to work. What would you do?