One thing that is often overlooked with these "egg eaters" is to partially debeak them. I know that some think that it's cruel, but it's an option that allows the hen to live out her normal life, versus the Sunday dinner route.
I have had good success with just taking about 1/3 of the top beak off. I also take a little of the lower beak (just enough that it's blunted off). They will bleed a bit, but if you have a styptic pencil, or other blood stopper, it won't be a problem. Also, the beak is somewhat tender for a few days, and the hen won't want to be pecking on eggs till the beak is fully healed.
I know that some on this board will think this option is cruel, but it works, and the hen is back to normal, less a bad habit in a week. Good luck!