Huh. Judging by Emilyko not remembering the first day she spoke to Kate, I wonder how much soot coffee was still in her system? Or if she was still being fed it. The pattern I've noticed seems to be like this.
-Brought in, given soot coffee daily.
-Begins work with their Shadow; at this point the Shadow has been left alone with books on how to be a 'noble', setting that foundation in their behavior.
-Soot coffee isn't drunk, but they're kept in isolation with their Shadow. Presumably as the coffees effect weakens, their personality comes through, allowing the Shadow to build their own personality. No outside influence.
-After a Debut, coffee is administered, and then repeated weekly, re-enforcing the brainwashing. But as we've seen, even the normal socializing type of brainwashing and buildup in the system carries lot of weight as well.