Why would she ask me deep questions, laugh at all my jokes, stare at me all the time then all of a sudden act nervous around me?

She acts nervous with me around but always stares and sometimes when I catch her she looks embarrassed and away. I feel like she’s changed her behaviour? I feel she is holding something from telling me?
Why would she ask me deep questions, laugh at all my jokes, stare at me all the time then all of a sudden act nervous around me?
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