After a girl rejected you, do they normally act this way?

A girl used to be really happy and friendly every time I saw her at work. As time passed I started to develop feelings for her as she was giving me signals or so I thought. So I decided to asked her if she had feelings for me, her response was a no with a gracious friendly smile. I respected her demeanor for being nice about it. Fast forward now every time I see her she ignores me and have a angry/ bitch*y face that says to everyone warning do not approach me. I just think is a waste of energy to be like, I accepted her answer and just be myself and continue to live my life normally. I am just curious how can a girl have changed her personality completely from always being nice and smiling to this. Can someone help me understand what is happening here? Because I surely do not. Shouldn’t I be the one to feel that way since I was the one that was rejected.
After a girl rejected you, do they normally act this way?
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