When a chicken is not feeling well, they go mute. They are also inactive, so your hen is probably okay. If she's having trouble breathing, though, you really do need to monitor her.
Open mouth breathing, a crinkly noise as she exhales, and dark grey or purple comb are symptoms of respiratory issues.
A normal hen that is on the verge of laying an egg is vocal and restless, often getting on and off the nest a few times before she settles down to relax and lay the egg. This can be typical of both seasoned and new layers.
However, sick chickens may sometimes find comfort in a nest box when they are sick. Look for the tail to be held low and flat when she's standing around in the run. That would be an important clue she may be having trouble passing the egg.