Standing too close

I was standing in line this morning for breakfast at the UGA dining hall. I was waiting patiently for the boy in front of me to pick out which piece of melon would be his when suddenly a brash girl darted up behind me in line. She was standing at an incredibly close distance and peaked over my shoulder at the strawberries. EXCUSE ME. I was here first. But of course, the non-confrontational side of me kicked in and a stepped only slightly forward in attempts to subconsciously tell her to BACK UP. It did not work and she prowled forward when I moved on to the berries. Rude. I just don't understand those around me who cannot simply identify social context clues.