Why does she touch my hand?

this girl I know, she seems like a friendly person, but I've noticed, when she talks to me sometime she touches my hand. one time she put both of her hands on top of one of my hands, she touched my hand then touched my shoulder seconds apart. She also seems like a touchy person, I didn't pay attention to see if she does this to other guys. Whats going on?
Why does she touch my hand?
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