It is difficult to know with certainty why an artist picks a certain theme. In "Annabel Lee," Poe's last poem, he continues, however, to explore a subject that has been important to him: the death of a beautiful young women.
Many critics and biographers have settled on Virginia, his young wife, as the subject of this poem. She had died of tuberculosis two years before, so like Annabel Lee, she died young. Like Annabel Lee, she was beautiful. The speaker in the poem falls in love with Annabel as a child, just as Poe did Virginia, a girl he married when she was only 13. Annabel was a "maiden" when she died, and some biographers believe Poe and Virginia never consummated their marriage.
While Virginia is the most likely candidate as a model for Lee, and while it is likely that Poe was grieving his young wife's death, it is important to keep in mind that a poem has a life of its own. There is not a one-to-one correspondence between Annabel and Virginia: a great artist's imagination will transform a subject.