You may have to cull. It is a very difficult habit to break.
If you know for sure which one, I would separate her. Give her some fake ceramic eggs she can't break and some plastic easter eggs that snap open and fill them with sand soaked in the hottest hot sauce you can find.
She may get the idea that eggs are hard to break and aren't worth it if she can.
At any rate, you have to get her out of there immediately before she teaches the whole flock how good they taste and you have to cull the whole flock.
ETA
It usually starts with a thin shelled egg that gets broken accidentally.