What was riddle on the library window? How did virginia solve it?

Painted in curious black letters, the six line riddle was about a golden girl who could win a prayer from out of the lips of sin and when the almond bore bears, a little child would give away its tears. Then all shall be still in the house and peace would come to Canterville. The ghost had requested Virginia to release him from the state that he was in. The riddle meant that in order to do that she would have to weep for his sins because the ghost did not have any tears and pray for his soul because he had no faith. Then, if she had always been sweet, good and gentle, the angel of death would have mercy on him. Virginia would come across fearful shapes in the darkness and wicked voices would whisper in her ear but they wouldn't dare harm her because of her purity. The purity of a little child was far more powerful than that of Hell. The prophecy foretold that a golden girl who was pure of heart would be able to bring about salvation for the ghost and he could attain peace only then.