The person who took the picture is presumably the one who wrote the caption, so unless they'd call their partner or their friends "this girl", we do in fact know that isn't the case.
Since this is an airport those lines are likely for different services, not just 3 options for the same service.
If something you're doing is annoying an entire group of people around you and they're all asking you to stop, then 9 times out of 10 what you're doing is inconsiderate. There's no good reason to just stand there ignoring everyone else instead of moving with the line and conserving space other than because you only care about how you personally feel on principle and your desire to die on a really stupid hill.
If her choice just affected her then that'd be one thing, but she's forcing her choice on everyone in line behind her regardless of whether they want to keep moving or not. If she wants to stand in place and wait so badly then she can ask someone in front or behind her to remember her place in line and let her back in later (most people are willing to agree to this if asked politely), then she can stand off to the side until her spot gets to the front, and go back to where she was once it's her turn, then everyone gets what they want.