Complex sentence: Count Volger tries to expose her gender unless she discloses the imperial message, but drops the attempt after some convincing from Deryn, who dares not to shake the confidence of Alek, who admires'Dylan' unaware of her masquerade as a boy.
Split into simpler sentences: Count Volger tries to expose her gender unless she discloses the imperial message. Deryn convinces Volger to desist, so as not to shake the confidence of Alek, who admires her as a boy.