So during the entire ending "our" Elizabeth is with us the entire time up until the point where we walk through the lighthouse door for the final time? We know this because she had the bird medal (I chose bird) attached to her necklace up until near the end of the ending (part where "our" Booker goes through the lighthouse door for the final time). After going through the lighthouse door for the final time we enter a tear that takes us to the part where Booker is about to be baptized (turned into Comstock) but you are surrounded by multiple Elizabeths and all of them have the necklace but WITHOUT the cage/bird medal who then proceed to drown Booker to prevent him from becoming Comstock.
-How is it possible for multiple Elizabeths (each one from a different universe) to occupy the same place at the same time (during the scene where Booker is downed at the very end)?
-Why are all of the Elizabeths (each one from a different universe) missing the cage/bird medal from each of their necklaces.
-Why is "our" Elizabeth not present during the scene where Booker is drowned at the end? Is it because our Elizabeth is still at the lighthouse because she opened up the tear which allowed "our" Booker to arrive at the final scene where he is drowned by the multiple Elizabeths from different universes?