"She does not know if she comes or goes."
Translation:Lei non sa se viene o va.
''Non sa se viene o va'' was accepted by Duolingo as it should, since the use of the pronoun is not only not necessary but not recommanded (as in not used by italian native speakers) even where the sentence would be gender specific in another language. You would only say ''Lei non sa se viene o va'' in a context where you want to highlight the fact that it is HER who does not know, not I, not you, not somebody else, but her. Other than that, the use of ''lei'' is not natural in italian. So in other words, it is not wrong to put ''lei'' in that sentence, but it is definitely not wrong not to put it :)