Brie's poem is about feeling unseen, so unseen that the speaker sometimes loses track of herself too. She opens with a blunt admission, "I am empty," and keeps her language plain and flat, as if she doesn't think she deserves anything fancier. Saying "there's nothing special about me" sounds less like boasting about humility and more like a tired shrug.
The ghost image is the heart of the poem. A ghost can be right beside you and you'd never know, and that's how the speaker describes herself. The final stanza repeats "empty" three times, moving from a bottle to a stomach to a heart. The bottle hints at drinking, though the poem only suggests this, and the last line, "after you," points to a loss or a breakup as the cause. The mood is quiet, numb and sad. Nothing is shouted. The speaker simply fades, and the short, trailing lines make that fading feel real.