I found one particular part of your conversation with her interesting. I have heard it several times. I think the way you respond to the thinking is key. When she says "Do you think you are smarter than the GB?", you said of course not. But this is not really about intelligence. From her perspective (and maybe yours depending on what you currently believe about the bible), its about truth. Truth wherever it leads.
This piqued my interest in the conversation as well. I remember , in a heated argument, I was having with my wife when she tried to take that tact with me. My response in that they had to put their pants on one leg at a time and wipe their asses after they shit didn't go down to well. Not one of them have any training or instruction beyond the drivel they claim as food at the proper time by mimic'd writing from colleagues for the decades preceding their ascendence to the corporate elite. That makes them as about as dumb as a box of rocks to me.
You're right in that it is not a matter of intelligence,but a matter of what is truth wherever it leads. But, the GB have it in the minds of JWs even a short circuit for that with the "wait on jehovah" mantra. If they are really spirit directed, inspired, or whatever euphemism of weasle words they are using to demonstrate that they are divinely benevolent, you'd have thought that they would get at least one thing right besides concocting more efficient ways of getting money out of their sheep.