It was a delicious, pointed response, skewering on the vapidity of asking such things, even if she didn't intend it to be.
Enjoy this video of New York Mag's Jonathan Chait explaining the vapidity of the "binders full of women" meme.
1650s, "flat, insipid" (of drinks), from Latin vapidus "flat, insipid," literally "that has exhaled its vapor," related to vappa "stale wine," and probably to vapor "vapor." Applied from 1758 to talk and writing deemed dull and lifeless. Related: Vapidly.