Even assuming she wasn't trying to make a point, and even assuming she's flown some (but not a lot) in the last decade, she could have gotten by without ID. If you're someone who flies 2-3 times every five years and forgets to or chooses not to carry ID now and then, you probably won't even remember the secondary screening you got last time you flew, or the fact that the airline checkin agent asked to see your credit card because you didn't have photo ID. And there's no way you'd have noticed the June 21 rule from TSA. People just don't pay attention to those sorts of things, particularly if they don't matter to them very often.

Similar case: in (approximately) the upper half of the lower-48, it snows pretty much every year. But every year, people seem to forget how to drive in the snow, there are more accidents after the first snowstorm than any other time, etc. Every year, the media and government issue releases to "teach" people how to drive in winter. If people who drive every day can't remember the details of how to drive in their home town 12 months ago, you can't expect them to remember to bring their internal passport/papers to the airport.