Why is she talking to other guys easily but not me?

She and I have had good conversation in the past. She will come up and make very small talk with me. But I've noticed she doesn't have conversation with me unless I'm alone. What is going on? Even she avoided sitting next to me but sat directly behind me. She has sat next to me before which was fine. I haven't said or done anything to upset her. So what is going on?

Why is she talking to other guys easily but not me?
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