After Johnny and Cora have sex, Johnny was grateful because she did the woman astride position, but Cora didn't get that that was woman astride position (woman being on top), and she said
"What, you mean on top?"
What makes her think that what she's doing isn't woman astride position?
My reading of the scene was that it was a way of contrasting her sexual experience (great) with her IQ (small). Simply put, although she has plenty of experience "doin' it on top", she lacks the vocabulary and the wit to recognise that that's what he's talking about.
Note that she also fails to realise that he's been to prison, imagining that he's been living in a monastery (!?).
This quite a common conceit in Hollywood films and her personality fits quite nicely with the TV. Tropes descriptor:
The Brainless Beauty is rarely the hero; they tend to be foils for more intelligent (though less successful romantically) characters. Some are sympathetic good-natured dullards, others are presented as annoying obstacles for our heroes. Either way expect a smart but plain character to be left fuming at the unfairness of it all.
A Brainless Beauty — even a sweet-natured one — is unlikely to be the serious love interest of The Hero. In fact they make a natural Romantic False Lead. It can happen though if the Beauty shows some form of Hidden Depths.
