Elizabeth finds some relief to sense the shift in Charlotte. Charm is something Elizabeth can do. She eased Songbirds worries with a song and with agreeing to his sole purpose. Returning her to a her tower. It's not what happened to her in the end, but it kept Songbird from killing Booker (if only so she could kill him later herself).

"It's good to know. No one would want an addiction. Thank you for telling me. Now I know better than to take it on my own without your medical expertise." She sets the vial down and lifts up the last set of bottles. "We only have the bottles of pills left. Can you get addicted to them too?"