She is visibly in command of that 'forum' at present. She dismantled David Letterman (or possibly more correctly helped him do it to himself) with just three sentences. Should she allow herself to descend to the level of pop culture, she'll be no more than a female Huckabee.
I think the thing with Letterman was grandstanding.
She had every right to be personally insulted, but to say his comment about her daughter threatened the self-esteem of millions of young women was hyperbolic and ludicrous, and the kind of thing that drives people away.
Instead of playing to every media outlet in the world, she should have simply called him an *sshole, then sat back and smiled. That would have been impressive. Understatement is more effective than showing up on the tube again and again and again, saying the same thing over and over.