He stares at her in silence for a full six rounds, weighing the probable value of being able to tell other Efreet the bare facts so far, as she didn't seem particularly eager to conceal from that devil who was eager to do her service, the crown on her head, Dispater's name, the loss to his pride and the effect on future bargaining if he concedes this much, the possible loss of profit if he scares off this customer.
...what decides him, in the end, is the number of other shops in the City of Brass; it would be all too easy for her to leave.