The sorrow. The closer she is to
The poetess feels as if she is about to die and there is nothing that can stop her death. There is not a single hope of life and she is accepting the death, and assures her loved one that everything is going be to fine. She also says that if her loved one gets busy in his life and do not remember her, she will understand that.
Earlier she wanted her loved one to remember her, but she now wants him to enjoy his life and remember her at the back of his mind, she loved him deeply and wants him to happy.
She says to her lover that it is ok to be happy and rejoice life without her. She realizes her mistake of asking her loved one to remember her. After her death if she will be missed by her loved one then he will remain in sorrow. The closer she is to her death, more caring kind and loving she is becoming.
As the feeling of death grows closer in Rossetti mind, the feeling of love grows stronger. She understands everyone has to die at the end even the loved once. Thus, we see love and death feed and thrive off of each other.
She stops being commanding at the end and asks her loved one with compassion to forget and smile anyway as she wants him to be happy. She doesn’t want him to be in miserable conditions after she is gone and ask him to move on and remember their good memories
Thus, we see in the first half that the poetess is very demanding and ruff, but later on as death approaches she becomes more loving and caring.