This question contains spoilers…
(view spoiler)[What happens to the persons who Nora replace in New Life? Where will they go until Nora goes back to Midnight? I understand that their mind will fill them up for the time they were missing. But my question is what happens to them during the period, Nora is in their place? (hide spoiler)]
Cocoa Boo As she's basically the same person, it's just her previous thoughts and experience living that life get muted, and the new Nora's thoughts take over. If she decides to leave, the old Nora's thoughts are re-awakened whatever time she missed may be a bit fuzzy....but it's understood that she'll just pick up where the new Nora had left off.
Normandy The author discussed the many worlds (universes) hypothesis but did not do a good job. In summary there are a huge number of Nora's in alternate universes that are independent of one another.