Thanks for the plug, Scott! Looking forward to your post!

Creative Screenwriting podcast has a good Q&A with co-writers Andres Heinz and Mark Heyman about Black Swan.

From what they said it seems that the original script - Doppelgänger I believe it was called - was very different to that of Black Swan, and Lily had a very different role and character in the drafts.

To me it seems the Lily characters from these drafts should be examined as different characters, not a development of one. If only because the fulfill very different roles in the story.

The podcast can be found here: http://feeds.feedburner.com/CreativeScreenwritingMagazine