That's what I was saying. I read a post similar to this and stopped mixing with my feed. It works for the rest of the chickens but not Bonnie.If you are providing calcium (oyster shells) free choice, just continue to leave it there so the chickens can self-regulate. As soon as you start trying to affect which ones eat how much, you will cause more problems than you solve.
If you were mixing oyster shells (or other calcium source) into their food, it is probably best to stop that anyway, regardless of whether the eggs are normal or not, and switch to providing it free choice. Too much and too little are both bad for the chickens, and they are usually pretty good at self-regulating.