I know, right? I was sitting here earlier thinking about all the times I can remember being flustered--teenage girl or not--and never, not once, did I ever grunt. That's just a bizarre way to phrase it.
*groan* -- nope, I also never grunt when flustered. As a teenager, I might have squealed, grained, moaned, snorted, giggled or uttered other high pitched or breathless noises but never a grunt; as a grownup more likely to go quiet possibly with a deliberate calming breath (and the occasional chopped off snort).