SPOILER ALERT
When Juliet first comes to at the bottom of the pit, she’s all upset, she tells Sawyer “it didn’t work,” that she hit the bomb but they’re all still stuck on the Island. Later, after Sawyer removes the big beam pinning her down and gives her a hug, she’s suddenly all smiles, she says “Let’s get coffee sometime–we’ll go Dutch,” she kisses him, says she’s got something important to tell him, and then dies, but Miles says she was gonna say “It worked.” Seems to me that the line about the coffee is something she will say to Sawyer in the alternate reality, and somehow she knows about its existence and that’s why she said it worked after all.