Girls, Why is she acting shy/nervous towards, but her eyes widen and pupils dilate when she sees me?

She is acting shy towards and seems a bit awkward towards me. But my mate saw her eyes widen and her pupils get bigger when she saw me. She was looking at me like a hawk. I've worked with her for 2 years and she was chatty with me and everything. Now she is being a bit tongue tied with me and I'm getting butterflies when I see her. At times she seems not interested in talking to me. So I ignore her and mind my own business but she ends up coming over to say hello to me.
Girls, Why is she acting shy/nervous towards, but her eyes widen and pupils dilate when she sees me?
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