Here's my read on Syril and Dedra:
Dedra was raised in an institution, where order and structure (and probably more than a little institutionalized conditioning) were likely paramount. For her, she felt safest when she was in control on her environment and her role in ISB seemed structured on maintaining order.
Syril was raised by a controlling, domineering mother in the more unstable. His personality ended up skewing to trying to create his own sense of order and control by combatting disorder common away from the "core worlds". His roles have largely been about creating order from chaos.
At Ferex, Dedra was placed in a situation she could not control, and it was Syril's rescue that re-established her sense of control (and he probably gravitated to her due to Freudian control issues stemming from his mother).
A big part of the Ghorman arc was how BOTH lost control and trust in the systems they held dear. Syril was working to maintain order (or so he thought), so the revelation that HE was actually the agent of chaos just wrecked his entire world view. Dedra, fearing another situation where she wasn't in control like in Ferex, didn't WANT to be directly involved with Ghorman, and her confidence was shaken. Syril, after finding out what the Empire was doing, felt betrayed by both the system AND Dedra, leading to the emotional outburst.
After Syril's death, Dedra came to the realization of how much the EMPIRE was the destabilizing element and just how little control she had. And with that lost of control, she lost probably the only other person she could love. I feel the culmination of the Ghorman campaign basically shattered her faith in systems she had spent her entire life to preserve and probably the only person she had ever, truly, loved besides her parents.
We will see where her character goes from there...tonight
