Just to follow up, Folly I believe can directly speak to beings that use Aetherial (sp, cause I listen to books on audio, not read) Energy -- so she can directly address Eferous, Cavendish, the Enemy, Predator, her crystal collections and ... Grimm. Grimm maybe very, very close to an Aetherialist while aboard Predator.
She also stated that she didn't talk to Puppets, even though she technically addresses Cavendish directly. Apparently, the "holes" in Cavendish are filled up with the Enemy, whereas Eferous and Folly have to do other things to fill up the holes. That's why Folly and Eferous are more benign, but also more broken the Cavendish appears. Other than her fixation on courtesy, Cavendish appears to be much more functional.