If a hen is laying, she is not really broody. Once they go broody they stop laying. Is it possible the other one is laying in her nest? I really don't know what is going on with yours. Silkies can be pretty strange about sitting on nests and going broody. With yours just being moved to a new location, it makes it even harder to know what is gong on. Does she spend the night on the nest instead of roosting?
It takes an egg about 21 days to develop and hatch once it is incubated. If a broody hen kept laying eggs after she started setting on the nest, then the first eggs would hatch, she would take those chicks off the nest to get food and water, and the other eggs would die. That's why they quit laying when they go broody. Same things happens if other hens are adding eggs to the nest. Also, if new eggs are added to the nest by other hens and you don't remove them, there will soon be too many eggs for the hen to cover so some will be pushed out from under her, cool off, and die. Then those will go back under her and other eggs will be pushed out to die. If she is really broody, you need to collect all the eggs you want her to hatch (Maybe buy a few from the place you got the two hens?) mark them, and put them all under her at one time. Then you need to check under her once a day and remove any eggs that are not marked. Your life will be a lot easier when it comes to hatch time and you will get better hatches if you do this.
Almost all broodies know when to get off the nest and eat, drink, and go poo. How often they do that and how long they stay off the nest kinda depends on the weather. If it is hot, they will spend longer off the nest. It should not hurt anything if you take her off the nest when you check under her once a day for new eggs and let her go take care of her business. I'd suggest checking to make sure she goes back to the right nest though, especially since she was recently moved ot a new home. Some broodies go back to the wrong nest. Silkies seem to be fairly bad about this, maybe because their broody instinct is so strong they are just as happy setting on their imagination as real eggs.
Good luck! Enjoy the journey. It can be really exciting.