Your being rational Oompa with a woman controlled by fear.
I lost my wife due to what the psykes call cognative disonanse. From her personal experience living with me she knew that I was not an evil man yet the WT said I was, no leeway: you leave them you leave Jehovah you are evil. No one can live with 2 such conflicting thoughts for very long. She needs to feel secure with you and not threatened.
Empathy: Say things like you understand how she feels tune into her feelings reassure her that you will not try to undermine her faith Find things to say like you admire her determination to stick with it: that she works so hard etc The time may come when she starts to question the WT herself then again it may not. If it does and she trusts you. When she brings up some issue where she thinks the WT is wrong tread very lightly Say something like. "Oh is that right I wondered about that myself then leave it". Don't think you have an opening to hit her with everything you know. Let her be the one to take these steps. Let her ask the questions.
I'll tell you a story about me the rational man. When my son was born I visited my wife in hospital and there were flowers everwhere everyone bought her flowers. So I thought she doesn't need anymore flowers so I never boughr any. Afterwards she would often bring it up and I would reply but you didn't need any flowers Untill one day 2 years later when she was visiting a sister in another city I sent her flowers through Interflora with a note saying something like Thanks darling for giving me a lovely son I heard later that she and her friend burst out crying and said what a wonderfull husband I was: She had got her flowers. Yeh I was rational and just plane stupid.