I think what may have led to the confusion is that in English terms such as "to depart", "to pass away", "to pass" are often used as euphemisms (polite synonyms) for "to die". Perhaps the translator was confused by Tolkien's tendency to use poetic language and assumed he really meant that Elrond and Galadriel had died...only in this case they did literally depart--on a ship!
This reminds me of a joke from a movie, in which a character mentions "my dear departed wife"
"Oh, is she dead?"
"No, just departed."
Did the translator do the translation of the book from beginning to end? If he had looked back at this passage after translating the end of the story it should have been obvious that the translation was not correct.