Girl standing behind me to stare?

For the record, no this isn't another question about "does she like me" "is this a sign" etc. I'm not even attracted to her, I'm just confused and honestly kinda creeped out a little.

I was waiting for the elevator at my workplace with someone else, and I noticed a girl looking at us while getting off the stairs, and then stood right behind me (plenty of space available by the way) waiting for the elevator back up.

I already thought that was weird, the elevator only goes back up where she just came from, but I was like whatever maybe she forgot something.

Then when the elevator came and I got in, she just started walking off out of the building while shooting weird glances at me with no expressions.

I don't even know this girl, super confused what that was about. Would love to hear what you guys make of this.

Girl standing behind me to stare?
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