can the oyster replace the cuttle bone, or do they need both. My female will happily eat the oyster shell but doesn't take much interest in the cuttlebone. Is this okay or does she need the cuttle bone?

i personly would provide both

does it matter if she only eats the oyster as long as she gets enough?

Is the oyster grit? I don't give that to my budgies. I believe they don't need it and it can cause crop impaction if they eat too much of it. The cuttle bone is good though as it keeps their beaks shortened and provides them with good calcium.

Do you have a cuttle bone in there at the moment? Because if you don't, you can leave one in there and after awhile she will try it. It just may take a while.

its not grit its pure oyster shell and yes i do have cuttlebone in there, i think she preferes the oyster