Narcissa killed the remaining time until the mudblood’s feeding, by having her student practice moving smoothly between the two positions repeatedly. She wanted to allow the pleasure chemical sloshing in her charge’s system to dissipate, so she found the smallest issues to nitpick. The combination of the hormone and pheromone regimen that the captive was unwittingly imbibing, as well as the artificially administered dopamine left her pet-project deliciously open to follow all directions unthinkingly.