"All those weeks that Tally had been lost in the wild, all she'd ever wanted was to be back here with Peris, pretty in New Pretty Town. It was totally stupid being unhappy today, or any day. Probably just too much champagne."
From the very beginning, we can see that Tally subconsciously has doubts about this new life in New Pretty Town despite her mind and her memories being altered. The unhappiness comes out after all and that unhappiness is definitely not caused by too much champagne.
"We are under control, Tally, because of the operation. Left alone, human beings are a plague. They multiply relentlessly, consuming every resource, destroying everything they touch. Without the operation, human beings always become Rusties."
Dr. Cable approaches Tally in an attempt to convince her to join the Special Circumstances. With the recent rebellious events in the New Pretty Town and Tally being the main face of those, Dr. Cable started to see potential in her to be a special. Tally, of course, refuses the offer as she knows the cruelty they are capable of. This is Dr. Cable's answer to her refusal and also her, and probably everyone else's in charge, justification of manipulating the people, even without their consent.
"A few tricks weren't enough to make everyone bubbly, she supposed; you had to want your mind to change. Maybe some people had always been pretty-heads, even back before the operation had been invented."
Peris chickens out at the last moment of everyone's escape and wants to go back to the easy life of being pretty. This is a turning point of Tally's determination to move forward. Her conclusion here holds more truth than she even realizes at this point because at the end we learn that Tally cured herself without the cure, because she wanted her mind to change.
