What does it mean if a girl lets her foot touch your leg?

You could say we're rather good friends. She invited me over to her house for an awesome video gaming session.

We were both sitting on the living room floor, and at one point, her foot occasionally touched the side of my leg. I'm unsure if it was intentional or not. (We both seem to be a little introverted in behavior, if that makes a difference.)

What do you people think this means?
What does it mean if a girl lets her foot touch your leg?
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