when you say she is laying eggs off and on for a month, you mean she's dropping eggs all over the place every couple days?
Are you providing a proper egg laying box? If she is dropping eggs randomly, that typically means she has no good place to lay eggs and thus she is trying to hold them in till a suitable egg laying spot is found. This can cause egg binding and this can be a life threatening situation. Even if infertile, ensure she has a proper egg laying container to lay all her eggs in.
There is no way to stop her from laying infertile eggs. If she decides she wants to lay infertile eggs, she will, you can't really stop it. Only way you can is to get her ovaries removed via surgery.
Make sure she has plenty of calcium, egg laying (whether fertile or infertile) puts a heavy drain on her calcium reserves. Make sure she has a good source of UVB, calcium and her insects are supplimented with calcium and D3. A healthy high calcium salad daily is good a well.
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PHLdyPayne