Girl raises her pitch in voice, what does it mean?

So this girl I've known for a while sometimes when talking to me she raises her pitch big time like almost hearing a little girl voice. Girls, why would she do that? It's only sometimes.

She also barely talks to me and I dk if she's shy. She's talkative to others though. I'm shy and don't talk to her much either so she might think I'm not interested in conversation.

What do you think?
Girl raises her pitch in voice, what does it mean?
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