The poem is entitled, 'They have taken away my Lord'. The poem reflects Mary's distress in a painfully realistic way. Jesus' cry from the cross might have been 'it is finished', but nothing was finished for Mary. She was left in the agony common to those who suffer the death of a loved one without any opportunity to say goodbye. Unable to minister to his torn body as it was taken from the cross, she was again frustrated when she found the tomb empty.
All funerals minister to the bereaved, rather than to the dead.
It is the living who need the rites of death to allow them to begin building new lives without the departed. In the poem Mary is in agony because she has been denied the burial rites, and so she is not ready yet to let him go. When the risen Jesus greets her, she imagines that everything is as it used to be. They will go back to the same old relationship. It takes Jesus' seeming rejection of her to make clear that their relationship has in fact changed.