No, if everyone acted like this it would be a tightly packed queue apart from one gap near the start. There would only be a gap behind her if she was moving too quickly for the person behind her to bother moving, and the whole point is she's not doing that. The one gap doesn't matter because of the barriers.
This is why I hate airports. She's right and her behavior actually makes it better for everyone, but people are too illogical to see it and get angry with her. There are simple logical solutions to every part of the airport experience, but people just do what they've always done or behave like dumb animals instead. Like rushing to be at the front of the boarding queue, when seats are reserved. Or crowding tight around the luggage return as if that makes your bag come faster, when if everyone stood back you could casually walk over and pick it up when it came.