It's all for show.

From time to time some of the women of the Show who have decided if they are going to play nuns in the pit they are going to act like them in private too, especially girls who ran away from their families to join the show. Most of them get over it eventually but some of them never do.

You however have known this 'Nun' thing was just a stage act from the time you were very small, after all, your mother was a 'Nun' right? How could a real Nun be a mother? So it is with you as well, you are a 'Nun' but only when the lights are on or the cameras rolling, the rest of the time you are just an under-hive woman, and that means you are looking for a husband.

Down in the under-hive people tend to marry young, sometimes as young as 15, but that's not technically legal without your parent's consent and your mother died when you were 10 and your father was never in the picture in the first place. That meant that since the Show was a stand-up establishment which followed the law rigorously so they could keep their charter, you had to wait till you turned 18.