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 november 2017
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If you want to sound fluent in English, then yes it is necessary. :)
4 november 2017
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Heb je je antwoorden nog steeds niet gevonden?
Schrijf je vragen op en laat de moedertaalsprekers je helpen!