Different people do it different ways. I’ve had success and I’ve had failure, but it normally works. I suggest you fix the pen she is going to, complete with food, water, and fake eggs or sacrificial eggs in the nest. Make the nest itself as dark as you can. Having the pen she is in fairly dark, or at least not in bright sunlight, helps too but the nest is the main thing. I go so far as to put a door on the nest so I can lock her in it and keep it really dark in there.
Move her at night after it is really dark with as little light and commotion as possible. Lock her in that nest that night, all the next day, and the following night. Make sure the nest is not in the sun where you are going to cook her. Open it up the following morning and see what she does. That pen needs to be locked so she cannot return to her old nest. Be patient. She may pace and look anxious, trying to get back to her old nest, but there is a pretty good chance she will return to the new nest and accept the move. There is always the chance she will not accept the move and break from being broody but give her time.
Before they go broody hens store up a lot of extra fat. That’s mainly what she lives off of while broody. She still needs to get off the nest to eat, drink, and poop some but they can stay on the nest for a long time without suffering. Keeping her locked up that first day is not being cruel to her, she can handle it.
If she accepts the new nest, wait two days to make sure, give her the eggs you want her to hatch. You can do this day or night after she has accepted the move. Remove the fake or sacrificial eggs and replace them with the eggs you want her to hatch.
Good luck and welcome to the adventure of broody hens.
