When beggars die, there are no comets seen; The heavens themselves blaze forth the death of princes.
I think that the symbol that can be seen here is the blindness. it it saying that it is like a sign in the sky. When she compares the stars and signs it is like they are only seen when you want to see them. When she relates it to when a princess dies, it is a huge sign, and when a beggar dies nobody even notices the change in the stars. its because of the peoples blindness that they will only see when a famous or rich parson dies, because they have no care for the poor