Hear Vala in the beginning of the poem:
"Hear! I will sing a Song of Death! it is a Song of Vala!
The Fallen Man takes his repose: Urizen sleeps in the porch
Luvah and Vala woke & flew up from the Human Heart
Into the Brain; from thence upon the pillow Vala slumber'd.
And Luvah seiz'd the Horses of Light, & rose into the Chariot of Day
Sweet laughter siezd me in my sleep! silent & close I laughd
For in the visions of Vala I walkd with the mighty Fallen One
I heard his voice among the branches, & among sweet flowers."
(Four Zoas 1:10-16, E 305)
So we can see that in Blake's myth Vala occupied the same symbolic role that Eve did in the Garden.
In The Four Zoas Blake used two kinds of daughters , who collectively represented Jerusalem and Vala:
1. Daughters of Beulah (Inspiration) are devoted to the well-being of man. They guarded the body of Albion in his mortal sleep on the Rock of Ages.
2. Daughters of Albion (Memory), obeying Reason weave the natural world of spiritual depravity.
In the poem Jerusalem we read: "The fallen Albion meets Vala and hears her say "Know me now Albion: look upon me. I alone am Beauty The Imaginative Human Form is but a breathing of Vala. I breathe him forth into the Heaven from my secret Cave, Born of the Woman to obey the Woman O Albion the mighty For the Divine appearance is Brotherhood, but I am love." (Jerusalem 29.49-52; E176)
And this from wiki : "Albion and Vala are deeply connected in Blake's myth. Originally, Albion was also with Jerusalem, but he abandons her after she claims that both Vala and Albion are too obsessed with the idea of sin. Jerusalem's fall provokes Vala to claim that she is the triumphant beauty and embraces materialism along with statements that women are dominant. Los rejects these claims and defends mankind. Although she has entered into a fallen state, from her line Jesus would be born. In the fallen state, she promotes revenge, jealousy, and justice during war. When she is redeemed after the Final Judgment, she is joined [as Jerusalem] with Albion as his bride. This allows for a union between mankind and the divine."