Now I know that potty training is difficult process and I understand not wanting to take your child to a public bathroom (although I've been in that library bathroom and it's exceptionally clean), but couldn't she have taken her daughter to the corner of the room? Or at least somewhere where she wouldn't have to navigate a room full of dancing toddlers while carrying a bowl full of pee? Yes, it was probably preferable to a puddle of pee on the floor, but I would have voted for moving away from the crowd, even if it involved a bit of fussing from my kid.
I mentioned this incident to a friend and she laughed and said, "I guess potty training is the new breastfeeding." She has a point. Some of us (including myself) nursed our children whenever they were hungry, wherever we were. I nursed in libraries, restaurants, even on the Wild Animal Park Safari Train without apologies. I was discrete, but I certainly didn't run off to the bathroom or cover myself with a tablecloth when it was time to nurse. Maybe with potty training you just have to whip out the potty when your kid needs it, no matter where you are. Of course what do I know? I've been sitting Baby M on the potty for 2 months now before his bath and when he asks to go (well the one time he asked to go), and we haven't seen a drop in that potty yet.