He tells her to hold tight, so Beverly does, which is at least preoccupying enough that she doesn't get too fixated on how close he is like this. It's necessary, and safer, probably, and it's hard to be anything but taken by the idea of this in the first place. Later, she can stop to be flustered by his proximity. For now, it's enough to try to swallow her nerves as he swings them up, a high-pitched noise in her throat, probably not quite drowned out by the rush of air around them.

"Holy shit!" she says, a little terrified but mostly delighted. Hearing about this is a far cry from actually experiencing it, but she trusts him. Besides, she doesn't really think he would suggest something like this if he were likely to drop her. That would be a pretty terrible end to a date.