Hope you haven't killed her yet, it is a pullet that will probably lay in a few days if she lives. A 20 week old orp should have developed the sex feathers in the hackle, saddle and tail indicative of a male. What you have is a pullet that has matured faster than your other pullets. On a rare occasion a hen will turn into a male but this has to have lots of factors to happen. Hens normally lay all their eggs from one ovary which develops, while the other stays small and undeveloped. If the developed ovary becomes damaged and the damage causes testosterone to be produced the underdeveloped ovary will be promted to develop but due to the increased testosterone it becomes a testicle, the hen will molt and grow male feathers, will crow and produce sperm, even though there is not a way for her to transport it.
I do not think this is what has happened here, even though your girl has a more develped comb and wattles she is still a girl, hold off on the chicken and dumplings and prepare for eggs and bacon instead.
Bo