What does it mean when a girl imitates you?

I have been spending a lot of time with this girl. We are not really friends but we talk a lot and have gotten to know each other. Because of that, we have absorbed certain mannerism from each other, mostly specific words or actions and we know what the other is thinking and how to respond and annoy each other.

Today though, we were talking and playing around and she did a good 2 minutes of "acting" like me, the way I act, the little things I do and how I say things, I was certainly impressed by how well she did it and started cracking up. She usually tells me she is not listening to me or cares about what I do, but it looks like she has been studying me for a while lol. What can I make of it?
What does it mean when a girl imitates you?
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