Or maybe you're more sanguine than me, and criticism doesn't bother you much in general.

I don't know about sanguine, but I'm probably more thick-skinned than you. I'm not bothered much by criticism.

Maybe I'm fighting the hypothetical, but in your example my first instinct would be not to get defensive, but try to figure out what is going on. Usually there are many ways to express the same idea and the way chosen matters. I could be assuming a too Guess culture, but such a bald statement by Sally looks like a breach of etiquette and those usually have reasons. It all depends on the context, of course, but my default inclination would be to suspect that Sally is bothered by something other than my dental hygiene.

But maybe I'm a bad example -- I don't react to criticism by going into a fight-or-flight mode.