In grading, professor takes into account submission time, performance compared to other students, and visibility of posters. Is it fair?
Why not ask your professor what she is trying to achieve with this grading before escalating? There is a clear discrepancy between how you expect to be graded (by common standards) and how your professor is actually doing that.

I understand your frustration, but I would like to add some nuances:


She is rewarding early submissions. She may be doing this to try to teach all of you better time management. It is debatable whether this is the best way of doing that. Given such a system I'd be a bit worried that a not-very-early submission could cause a failing grade.
She is grading off a standard as set by excellent students. In the US, it's very common to grade on a curve which inherently contains a comparison with fellow students. However, the details are typically different.
She is rewarding visibility/popularity. In industry and science, these are also commonly rewarded. One could even go so far as to say that securing a poster position close to the door is part of increasing visibility, although I think that's overly harsh.


All in all, I think your professor has some good ideas but her implementation leaves something to be desired. Also, all of this should be clearly stated in the syllabus. I'd have a conversation with her about this, possibly argue for a higher grade for yourself, but I'd very much consider how much time and effort you want to put into this after that.