Why's she act like this?

I have a friend who the one time we hung out, she was nervous to the point she wouldn't walk beside me and kept messing with her hair. We haven't hung out since how we both work, but she's bought me drinks a few times and I've caught her watching me, a few times. I noticed if we're talking, she runs her hand though her hair and makes a lot of eye contact.
Why's she act like this?
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