I believe that when the man and the girl say, "Everything tastes like licorice," this can be considered a metaphor, even though it contains the word "like" and might be construed as a simile. Everything does not really taste like licorice. Saying that everything tastes like licorice is implying that everything in life turns out to be a disappointment.
"Yes," said the girl. "Everything tastes of licorice. Especially all the things you've waited so long for, like absinthe."
In this instance the word "like" is not used, so it is even more of a metaphor. It is an ingenious one. Hemingway is using a simile, or an analogy, as a metaphor.
The title of the story is "Hills Like White Elephants." The hills may look "like" white elephants, but the whole simile is also a metaphor. White elephants are symbols of anything of great value that is not wanted. The hills may be "like" white elephants, but the white elephants are metaphors for the unwanted baby which the man is pressuring the girl to abort. It is obvious throughout the story that the girl wants the baby and the man doesn't.
Another thing about white elephants, which may affect the outcome of the conflict, is that a white elephant is only a white elephant because you can't get rid of it. If you could get rid of it, it would no longer be a white elephant. So maybe the man will not succeed in persuading the girl to go ahead with the abortion after all?