I'm wondering if I should submit this alternative: The woman eats her second apple. There is no possessive pronoun in the Polish sentence, but it's a natural thing to say in certain situations. For instance, if the woman brought a basket full of apples for lunch and she's just gobbling them up, I'd easily go for 'her second apple'. Otherwise, the translation seem to imply that there are several apples and she picks one specifically.
So my question is whether Kobieta je drugie jabłko. only translates to the latter, or to both :)
I'd say the impression without context here is that woman has already eaten one apple and now she eats new one. I wouldn't assume there is a row of apples ans she eats the apple nr 2, or she picks two apples from the tree and eats the one she picked as second. (Those are valid translations but not natural interpretation without context)
Assuming the sentence in Polish means the woman has already eaten one apple and now she is eating another one, "eating a second apple" seems to be the most accurate translation. You could also say "eating her second apple".
To me, "eating the second apple" only makes sense if this particular apple is second in some other sense (e.g. the second one harvested this year). It implies that if she had eaten a different apple, she wouldn't be eating the second one, because two different apples can't both be the second.