Dating

Why is she doing all of this?

So there is a girl at work I kind of like. Whenever we pass by each other in the hallway, three things can happen:
1. She looks at me and makes eye contact, holds it and then looks down.
2. Looks at me and quickly looks down and even sometimes moves her head.
3. Avoids looking at, keeps looking to the side and down...

But when we talk, she makes very long eye contact / long gaze...
Why is she doing all of this?
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