She doesn't know, she doesn't care, she didn't notice, she couldn't pick you out of a lineup if you where the only guy in it, she was not paying attention to you or judging you because to judge you, she'd have to care about you at all. She does not care about you at all. You're some guy who walked down the hallway at a similar time to her, nobody cared. At all.
Body language can be a bit misleading sometimes. For example, a few weeks ago I was hanging out with a girl after class. She would constantly walk behind me, no matter what I did. If I slowed down so we could walk side-by-side, she would slow down even more so she could be behind me. It was SO frustrating...
I think you're overthinking it. Not overthinking anything will produce better body language anyways. Believe it's okay to be yourself and react however you see fit.