If you're attempting to find a productive rhetorical truth in a piece about shedding productivity as a focus, you're missing the point.
In fact, you're arguing that she should 1) be able to quantify happiness, 2) consider life-expectancy as a proxy for life quality, and 3) pursue optimizing life by quantifying and measuring it. I think you're missing many points.
The whole idea—the wisdom, if you will—is that you lose an extremely precious thing by focusing on measurement and optimization and increasing quantity and productivity. She has an extremely clear and valid point, which lucidly carries so much truth in it, and is not particularly hindered by slight rhetorical mistakes or lack of clarity. It's that true.
In fact, the clarity and style and beauty of this piece remarkably matches almost exactly how it feels. It's so confusing and seemingly contradictory and paradoxical, yet we know it's true. Even so, no one knows what, exactly, to do with it; so we call it unproductive and go on trying to live our highly productive lives. It's so much bigger than we are, this thing, and resistance seems futile.
And this is when you begin looking into Zen, and things become clearer and muddier at the same time, but you have a fleeting chance, at least, of converging on the ability to hold a thing in your head that's both true and false at the same time, and come just a bit closer, thereby, to the reality of things.