the thing is , she can but why is she being pay under the table in the first place , is she here illegally? if that the case she can threat her employer that she will tell the immigration but that won't do her any good , she might end up being deported back to her country , what she can do is talk to her boss nicely and ask to see if she can get pay for the overtime work , if you are under the table , u can play games with the person who hire you but in the end , you will both get hurt , it's not worth it , i was hired under the table 8 years ago and same thing happened , i was working at a restaurant at the time , i understood that u cant really control the hour of the staff if some customers want to dine late but it wasnt fair for me so i talked to them nicely , they didnt give me any raise but i get to go home on time