How does H.H. describe his relationship with Annabel in the novel, Lolita?

H.H. fell in love with Annabel Leigh around the age of thirteen. They experimented sexually, but they never had full intercourse. Annabel died four months after their last attempt at sexual involvement. H.H. never got over Annabel's death, and he thinks that that may be the cause of his obsession with “nymphets.”