There is a girl in my grade i accidentally look at often. So today in lunch she thought i was looking at her (i wasn't) and she got up and told me to turn around and stop looking at her in front of everyone. I am embarrassed and don't know what to do?
Lol you don't accidentally do anything often. Stop staring at her
You should have come back with:
"Oh. You want me to look at you when nobody else is around, then?"
Well it is too late to do anything now, except sit with your back to her at lunch from now on. If she decides to yell at you again, just let her know you weren't looking at her and that she has quite the ego if she thinks everything is about her.
Try not to worry about it. I mean your probably a nice person and she is stuck up. It'll be alright. You'll be alright.