Girl's Behavior

Why is this girl a bit introverted with me but is starting to make small conversation with me?

She and I are having moments when we are standing close to each other, she is offering to help me with tasks. Even in so training tasks she and I are naturally just partnering up in pairs for training tasks. She even is teasing me a little. She teased me about the fact my jacket size was out of stock and that I should have ordered a small size like her. It was just a joke though. Plus she was laughing at something that wasn't working out for me as joke. She said ' sorry I shouldn't laugh". I laughed too and said " none taken this is going to shit". Then she offered to help me.

Why is this girl a bit introverted with me but is starting to make small conversation with me?
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