Mmm, well a black rock [assuming she is not geriatric] should be laying virtually every day or that's what it says on the tin! I have never had any though I did try & get some earlier this year there were none available in these parts.
If you are worried I would suggest isolating her & giving her treats like bread & milk & cheese - for the protein & seeing what happens.
Any signs of moulting which would also explain the lack of eggs but unusual if this is her first year.
