People always say "why does nobody speak up anymore" but then when someone actually does, the rest of us just stand there like statues. It's the same pattern I see everywhere now - at the gas station when someone cuts in front at the pump, at the coffee shop when a person slides in ahead, even on the highway when a guy forces his way into a merge lane. Everyone is too scared of a confrontation to say anything, so the rude people just keep getting away with it. But here's the thing, that one person who called her out probably made that woman think twice next time. It's not about winning an argument, it's about not letting the line become meaningless for the rest of us.
Ugh, that's the worst. I actually spoke up one time when a lady did that at my grocery store. I just said, "Excuse me, the line starts back here," and pointed. My heart was pounding, but she mumbled sorry and went to the back. It felt scary but also good to not just take it. What's the point of waiting if people can just skip?