Rossetti gives her loved one permission to remember or forget her once she's dead, and acknowledges that she will no longer be aware of what transpires in the world once she is buried. She goes on to indicate that she believes in some sort of immortality of the soul with the phrase "And dreaming through the twilight/that doth not rise nor set", but it appears she does not hold out hopes of heaven or belief in hell, and is uncertain what sort of consciousness her own soul will have - maybe it will remember her loved one, maybe not. To me, this is the reading of the poem on its face, which I find fascinating because Rossetti has a reputation as a devout Anglican, who refused to see one of Wagner's operas because it was based in paganism and gave up chess because winning gave her too much pleasure.