If you still have all the birds in one cage, that is your problem. Breeding birds need to be kept as one pair per cage. Other birds can be viewed as rivals or as a threat. Breeding birds need privacy and while you can have other breeding birds in nearby cages, some birds will not settle down to breed if they can see other birds. In this case you need to put some type of barrier between the cages. If you do have all four birds in one cage, the female probably feels threatened and she will keep eating the eggs as long as the other birds are in the same cage.
If this pair is alone in their own cage, then unfortunately she has developed a very bad habit that some hens will do. It can be due to poor nutrition but it may be simply because she likes the taste. Breeding birds need a nutritionally balanced diet such as pellets or other fortified food. Loose seeds will not provide the nutrition they needs. You can also offer fresh chopped veggies and fruits, multi grain bread and cooked eggs, with the shell included. I would take the nest box away and if needed, improve their diet. Otherwise, rest them for a few months and then try again. Meanwhile offer her some scrambled eggs daily to see if she will learn to eat these instead, When you set them up again if she continues to break the eggs, I would take away the box and give up on breeding this bird. Sadly once they start breaking and eating eggs, many will never stop.
Thank you for asking Lafeber,