they may have just broke and when that happens they will eat the eggs. you might take the eggs from her and put them in an incubator, but if she is eating them and they are broken, are they even fertile?? how long has she been setting.. and have you candled the eggs??
could another hen be getting in the nest with her? sometimes we have some that try to get in the same nest at the same time. maybe she is just hungry? can you put food near her?