"O bir kelime bile söylemedi." Translation: He did not even say one word.
I understand the Turkish "bir" in English equates to "one" & "a."
"O bir kelime bile söylemedi." - She did not even say a word. - Correct.
I cannot explain why this answer would be rejected by Duo?
In other Turkish Duo questions "bir" goes after an adjective & before a noun.
Beyaz bir araba. - A white car. Bir beyaz araba. - One white car.