The direct translation of 'a daughter's love is eternal' in Latin is 'filiae, occisus est a quoniam in aeternum'.
However, just a slight change in the original sentence can show you how difficult in can be to translate English into Latin...
If you amended the English phrase to more formal 'the love of a daughter is eternal', in Latin this becomes the simpler 'filia, amor aeternus.'
The word filia in Latin means daughter and is where English gets its word filial, meaning of children or the family, along with the Latin word for 'son', filius.
In our original Latin phrase, 'occisus' means killed, 'est a quonum' translates as 'by since the' and in aeternum' is forever, so you can see how different Latin and English sentence construction can be, even though so much of English is based on Latin.
For more Blurit translatins of Latin phrases, check out: In Latin, How Is The Phrase, "Together Forever In Eternity" Spelled Out? and How Do You Spell Sister In Latin?
Or go back to school and learn some conversation Latin with this teacher's YouTube video: