I dunno, I've seen people colour, and gasp, and bite their lips. After all, what is the breath caught in the throat but a gasp? It's the body language of teenagers and essentially many of the protagonists are teenagers, or only just out of their teens. .I am not sure if this is due to having gone to an all girl's school with a rather rarefied atmosphere where boys were strange alien beings. It could just be that co-educational girls are less likely to find things to blush about, or show shock or shyness, because if they were going to be shocked they got over it when they were about 10. At least, the language of many young teens of both sexes is enough to make me blench at times. And we Brits aren't mealy mouthed as a whole! And I confess as well as blenching, my breath caught in my throat from sheer shock as I glared pointedly at the string of obscenities from the mouth of a fairy-like child of about 4.
I usually give pointed looks [generally with one elevated eyebrow] if I think a conversation is running out of the savoury or meandering away from the actualité.
Maybe it's just a feature of the period, when girls particularly were more sheltered? though I can certainly feel myself colour up if I've done something remarkably and embarrassingly stupid. Like putting the peeled sprouts into the washing machine and trying to cook socks.
(nfm)