Eh, I don't think they put her up there tonight with any grand ambitions, but probably would have had the wife of the nominee speak, no matter who it was. Just another voice of women to be recognized, just another flavor, all are equal, just like the Oprah audience, where all voices are listened to, regardless of content, as long as they aren't too extreme. This is the milktoast convention, the message is 'see how normal and tame we are' and 'see how we are just like your ordinary neighbors', so a boring speech by her in a living room voice fits the bill. Not what she said, but how she calmly said it. Thus I doubt that they are going to push THK as 'the smartest woman in America' the rest of the way, but perhaps more like an above average smart wife with some strong opinions, 'just like most women'.
Plus some would label a sizable portion of the Dem's female demographics as "irrational, sexless, boring, and self-centered". Often quite sensitive about their irrationality, and thus any criticism of THK is a criticism of them. They may not relate to much of THK's real lifestyle and ideas, but if her appearance succeeded, they can relate to enough of what they saw. Another way to subtly try and set up for another Lazio effect.
Or maybe she parlayed Alexander Polier into a keynote speech opportunity...