"And they lived happily ever after."
...is probably not the postscript to "Hills Like White Elephants."
In the story, Jig seems to want to get married and have a baby. However, the American man seems to want her to have an abortion and for them to then continue the relationship as it was before the pregnancy. Neither of these options seems acceptable to both parties.
This impasse leads to the communication breakdown shown in the final two lines of the story. The man knows Jig doesn't "feel better," but asks her anyway. She responds by pretending not to know what he’s talking about. In light of her previous request that they not discuss it, her response isn't out of character—but it also doesn't seem to be getting them any closer to a solution.
If the fact that that the story is part of Hemingway’s 1927 collection Men Without Women is any evidence, the end is nigh for these two lovebirds. The breakup of their relationship could occur in one of two ways: 1) they get married, have the baby, and then break up, 2) they have an abortion and then break up.
Either way, it's hardly a fairytale ending.