By now Brenda understood her vanity was -- well, not just for vanity's sake. Instead it was sort of an organizing principle: a way to check and see if she was still here. Confronted by turbulence? Check your hair. Appearances were easier.
And maybe that was how it was for everyone, or nearly everyone. They didn't expect it to actually work, i.e. that they would be beautiful, and therefore beloved, and therefore all right.
Anyway, one's own decay was easier to haggle and bother with than everyone else's. To say nothing of the dissolution of the world.
Nowadays a woman who didn't smoke and ate greens was likely to outlast major geographic structures. She might easily make it to 2050, longer than nearly any glacier or coral reef. She would outlast the polar bear, perhaps the honeybee, or even tuna fish.
Considering this, it was easier to puzzle out how to look human, than how to act it.