"The eighth girl is my girl."

Translation: A opta fată e fata mea.

[olb38]

Will be acsepted like correct answer " a opta fata e a mea"?

[hptroll]

I believe it is grammatically correct and actually a better way of expressing it but it does not respect the English sentence. What you wrote would be “the eighth girl is mine” in English.

[olb38]

Why here we must repeat "fata"? I am bulgarian and we can just say the eighth girl is my" and will be enough to understand that we talk about the same object " the girl"

[illexsquid]

(The same reason that hptroll gave above.) In English we can say "is mine" and that is equivalent to Romanian "e a mea". But the English says "is my girl" so the closest translation would be "e fata mea". The meaning is the same, but the words are slightly different.