That even unto death I would await you by my post And would never lose heart in the tower of silent watching (13-14)
The speaker's sure of one thing: no matter what happens, she'll wait for her sweetheart. That's her main plan—to be there for her hubby, and wait for him, no matter how long it takes (even if she has to wait until death!).
…Oh, at last, when you return through the three Pa districts, Send me a message home ahead! (27-28)
Here we see the speaker expressing her hope for her husband's return. She speaks as if her husband will definitely return (when in fact we don't actually know that he's going to come back, considering how long he's been away). By addressing him directly in these lines, we also get a sense of how much the speaker desires to be able to communicate with her hubby.
And I will come and meet you and will never mind the distance, All the way to Chang-feng Sha. (28-29)
Again, in these final lines the speaker projects her hopes and dreams onto the future. She imagines going to welcome her sweetheart on his return home. While this is a point where the speaker expresses optimism about the future, there's also a sense that her hopes and dreams may not be realized. She's hoping for her husband's return, but we don't actually see that return happen in this poem.