What does it mean when a girl puts her elbow on a guy's shoulder?

The girl did this to me randomly. she's a mature and nice girl. She doesn't seem like the type who would do this to everybody.
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+1 y
Just know who she is. She's from work. Know her for a short time. See her around rarely as we work in different parts.
What does it mean when a girl puts her elbow on a guy's shoulder?
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