It was only a block later that I realized I hadn't waited for her to respond to my question before seizing her bag and lifting it over the turnstile. I was being completely presumptuous. I imagine she gets that quite a lot, people don't tend to take little people as seriously as we should because of their size. That doesn't excuse me being a jerk. She is an adult and it's possible she would rather struggle to get through than accept another person's help. That's certainly her choice. I should have respected it and waited for an answer.
Of course what I did is hardly horrible, but it wasn't conscientious or thoughtful. Those are two things I strive to be. And in this case, I failed.