You're not saying she purposely brought forward an EVULZ plan to let the Orb dumb down her mental-status to Gul'dan's doll right?
What's very probable is that the Orb began to do its thing right from the moment she took it and brought it away for "destroy it".
All in all it's still Cordana's fault in a way, her sound files kinda imply that the Orb played on her nonsensical concerns about Khadgar's "methods" and sky-rocketed that shit to the heavens, which is kinda stupid considering Wardens don't really seem the kind of jailors who go easy on their prisoners.