There is no way for a pullet (young female) or a hen (older female) to turn into a rooster. Many times a dominant hen will "crow" if there is now rooster around. We have had two hens that have done that before we got roosters. But they are very much still hens, and they still lay. Hope that clears it up.
Of course they don't. Someone in the flock just might take over the "head hen" role, though. Occasionally a hen will crow. But she remains female and lays eggs.