They do it for many reasons. One could be lack of protein. You can try feeding BOSS (black oil sunflower seeds) or some cooked meat scraps. You also need to get out there and collect the eggs frequently!
Mine all eat the same diet.....only having a problem with one of mine eating her eggs.........drives me nuts.I go check quite alot during the day to make sure she wont have a chance .........but she beats me to it everytime? wish I knew the answer for you and I both !
Egg-eating is a bad habit some birds develop. You want to remove the one hen that is doing it, or else a few others may catch on to the tasty trend.
Sometimes egg-eating can be solved by placing golfballs in the nests. There are many solutions to this problem suggested by many people, if you do a search you will find a TON of info on the subject.
Some people just cull the hen and get it over with, others choose to try and break the habit first and use culling as a last result.
If you decide to rehome her, be sure to be honest and let the next owner know the hen is an egg-eater. Honesty is the best policy. There have been people here, who have bought birds over ebay only to end up with a flock of egg-eaters, they were dissapointed to say the least.
I wish you well in breaking her of that nasty habit! I would try to separate her while working with her, to avoid her teaching others just how tasty those eggs are.