Well since you mentioned Sam Harris, I will try to narrow it down and operate from his framework. In his lecture-version of 'Waking Up,' he explains at length what he means by discursive chatter. This explanation I will give a nutshell for, but I highly suggest purchasing the lecture if you can.

Harris's definition of 'chatter' may apply to you, even though your wife may have a different or more obvious version. His example is this: you are very thirsty. You see a water bottle.

You think, 'Ah, yes! I'm so thirsty.' Or perhaps you visually are a thinking in the form of a memory of the day's thirst that pops up as you walk toward the bottle of water.

It's that pattern which is like a news report that we almost never need but. We are almost always receiving in some form (if not the verbal form). Something 'in you' already knew you were thirsty, and yet another thing in you was 'reporting' - either verbally or visually or emotionally - the old news that you are, yes, thirsty indeed.

It's that subtle, unnecessary news report that Harris is talking about. Obviously as an author he isn't saying to destroy thoughts, just to alter our relationship with this 24/7 news report pattern.

He calls it 'discursive thinking' because many traditions describe the 24/7 news report as if you are in 'discourse', but with someone who isn't there and doesn't care that you don't need the info.

I hope this clears things up a little, and demonstrates that 'inner chatter' is not only verbal (though your wife's version is the most common and easy to spot).

Good luck, I would like to know the other questions you had 'queued up' after reading 'Waking Up.' I read it and am fairly cognizant of Harris's overall works.