As a cat owner, I can completely understand this woman. Especially when my cats were kittens. I would be completely antisocial just so I could spend every waking minute with them. I stopped hanging out with my friends after work just so I could race home and hover a string over their heads. I totally get the need to be with them all the time. That means even taking them on the subway.
I'm sure the little buddy is a little scared, but maybe she just picked him up and had no choice but to take him home on the subway. What else are you going to do? Right next to your boob is just as safe as any place else. It's not until later when they're older that they can squirm away from you.