How does concentric antenna wire cross the antenna in a wireless card?
It looks like nothing special is done. See xray and other teardown.

I would say that the localised bending is probably small enough, and limited by the nearby inflexible chip, that this turns out not to be a problem. The cards do have a limited life of a few years, and although they're flexible people don't actually routinely bend them that much - the plastic itself is susceptible to bend fatigue.