But Dedra did change as a direct result of her experience on Ghorman. Dramatically so.
Prior to Ghorman, Dedra did everything by the book. She trusted in the Imperial system. She worked hard to get her superiors to sign off on her inquiries into Axis, because she was convinced she was in a meritocracy. She was sure she would succeed in the end, because she was sure her competence would be rewarded.
Then Ghorman happened. Dedra realized she wasn't in control of anything. The Empire was using her as a pawn, the same way she was using Syril as a pawn. When she realized this, she figurative choked on the constraints placed upon her by her position as a loyal servant of the Empire, as represented by her uniform's collar. (This was shortly after Dedra was physically choked by Syril in the final act of their relationship, a parallel event which established the relevant metaphor: being choked by someone or something represents no longer being in control of that person or thing.)
Fast forward to Krennick's interrogation of Dedra. We discover that, in the year since Ghorman, Dedra has become a "scavenger." She's no longer asking permission to investigate Axis. She's gathering information outside the normal chain of command. As a result, she discovers classified information about the Death Star, none of which is intended for her.
Dedra's experience on Ghorman changed her in a way that ultimately lead to the revelation of the Death Star.