More and more time passed, and still Sophie didn't show.
It was even easier than Esme had thought. With a little manipulation, she was able to harness the power of the four-in-one in the efforts to control Sophie. No one was more intimate with Sophie's mind than the Cuckoos, no one. Not Emma, and not Quentin. He may have found her wavelength, but the Cuckoos had lived within eachother's minds for years, now. As long as Esme played her cards right, no one would be able to detect the intrusion.