The Poet
The speaker in a poem is not always the poet herself. Sometimes the poem is shaped by a point of view that differs from the true author, for artistic effect. In any case, the speaker's personality is on full display in the poetry. She feels tainted and unclean, and is working through feelings of guilt and envy.
Snow White
Snow White represents a lot of things, but she doesn't represent a human. Rather, she represents the ideal life that is depicted to young women in princess stories, and she represents the fortune and blessing that the speaker feels her own life lacks.
God
There is poetic language in "Pyramid of Bone" that suggests God's involvement. More accurately, the language reflects that God itself is responsible for the plight of the poet. The poet is directly questioning why some people are blessed like Snow White, while some seem cursed.
