Some people don't teach their children YOUR version of manners. They teach them their own version of good manners. If you feel so strongly that children giving up seats to adults is the only correct behaviour to have, then why not say something to educate her? Wouldn't you be doing her a favor. Why passively fume in the children's section and just hope she gets the message? Why not passionately defend your RIGHT to the chair?
I am exasperated by this discussion. Does that make you an exasperating person or does it just make me easily exasperated? Project much?