"No girl is eating her fish."
Translation:Kein Mädchen isst seinen Fisch.
Why is "seinen" a correct translation when it is "her" fish and not "his" fish? My answer (ihren) was accepted.
Das Mädchen is neuter and neuter uses the masculine conjuction of the possisive pronoun. It's more common to use the feminin conjunction though, that's why your translation is correct.
The same thing happened to me. If I remember correctly, Fisch is masculine; and in this case would be accusative? If that's true, ihr would have to take on the accusative masculine -en ending. Just like der Fisch turns into den Fisch, ihr Fisch turns into ihren Fisch. I hope this helps. If I was wrong or someone can explain it better, please correct me.