I try to not give advices on health issues to be honest.
On the other hand, this might be a simple issue also.
I would definitely try Joog's advice on seperating the hen for a while to see if there is a change.
Also, inspect the nest very closely.
Sometimes, the hens lay eggs with out shell and it gets smashed into the nesting material quickly.
This can be very rare and due to an exreme case of calcium dificiency.
It doesn't hurt to provide some calcium suplement.
If these don't help (unless someone else has a different idea to try) I would say it is a good idea to show the bird to a known avian veterinerian.
It could definitely be a symptm of something internal/desease etc.