I wouldn't say it is incorrect or correct.
The way that sentence is generally said would be more like:
If she had arrived yesterday, she would have been here by now.
4 listopada 2017
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If you want to sound fluent in English, then yes it is necessary. :)
4 listopada 2017
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Nadal nie znalazłeś/łaś odpowiedzi?
Napisz swoje pytania i pozwól, aby rodzimi użytkownicy języka ci pomogli!