"La fille est sale."
Translation:The girl is dirty.
I am not sure because I cannot see the page of your exercise, but "la fille est sale" is indeed "the girl is dirty".
if the French was "ta fille est sale", the English would be "your daughter is dirty".
if you have no detail about "la fille" (like a possessive adjective or a complement like "la fille de Mr XYZ), it has to be "the girl" and not "the daughter.