why is the sentence " ela ensina a filha" not Ela ensina a sua filha? It is translated as “She teaches her daughter.”, but it says “She teaches a daughter” are we to intuit that it is her daughter?..
Kate.
I believe that “She teaches a daughter” would be “Ela ensina uma filha”
But in the context of the statement in question, “a filha” and “a sua filha” are I think both correct with maybe the former much more natural. I am sure that Joseph or Molly will come to our rescue!!
Pesky language is Portuguese…I am currently wading knee deep in the Imperfect Subjunctive tenses. Ouch!
Mac
Olá, @kateevans00. You can say it both ways. You can even say “Ela ensina a filha dela”. But saying “Ela ensina a filha” sounds more natural and practical. Unless anything points to the contrary, you should presume that it’s her own daughter 
By the way, as @mac.cummings explained, the literal translation of “Ela ensina a filha” would be “She teaches the daughter”.