Earl Schulze argues that Shelley, in lines 323-44, is depicting the rebirth of his poetic self. Emily "is Venus fully humanized, the integrating power of the poet's imaginative life. No longer a phantom 'forever sought, forever lost,' she is a new sun of a transformed world, or, what in Shelley's poetry is the same thing, a fully-developed, mature imagination" (213).
Schulze, Earl. "The Dantean Quest of Epipsychidion." Studies in Romanticism. 21.2 (2002): 191-216.