That's good it was thin shelled, it probably broke by accident then.
Time will tell if she has decided all eggs are food. If you don't already have some, put a few wooden eggs in the boxes to help discourage her from trying more eggs, or house her apart for a little while with some wooden eggs...
Sorry to hear it. At least you know who is doing it!!
Unless the egg she was eating was a soft shell or this shell egg, you may have to separate her and try a mustard egg on her to see if you can break the habit.