Why does this girl always invade my personal space?

I'm 16 and I work with a girl that 17. I don't work with her a lot but we usually see each other when I'm clocking in. She's usually talking to someone so I don't really say anything, but when she's not she talks to me a little. Nothing flirty, but friendly. I've noticed, she's always close to me. I was standing by a trash can one day and she put something in it. I was right beside and my private was near the opening. She put her trash in it without saying excuse me. It was really awkward lol. Yesterday I was standing in line about to clock out. It was only one person in front of me. She came in the room and started talking to the person in front of me. The weird part? SHE STOOD RIGHT BESIDE ME! It was really weird. She was about 2/3 inches away from me. I could have put my arm around her if I wanted to. She didn't even look over or say anything. After about a minute the person she was talking to walked out with her. It was really strange. What's this girls deal?
Why does this girl always invade my personal space?
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