Get some hard plastic nesting eggs (if hollow, fill with sand) or wooden nesting eggs. Put them in the nest and on the pen floor. After they peck on them for awhile and discover they can\'t be broke, it may help. The other thing you can do is place her in a rollaway nest early each morning, so as soon as the egg is laid it rolls out behind where she can\'t reach it. Something like that can be easily built from wood and wire. She only needs to be with the rooster a few hours each week.
That said, if you only have the one pair, and no doubt they are related to begin with, you probably need at least another pair to keep from too close inbreeding down the road. But make sure the new ones don\'t pick up the bad habit from those you have now. You may need to keep them separated.