Why would a girl post a lot of pictures of her with guys if she is talking to a guy?

My brother is talking to a girl who he followed on instagram but she hasn't followed him back. They text basically every day and snap chat. She invited him to a party and posted pictures of her with other guy friends there but not him.

Again, just weird.

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Edit: this should be under girls behavior not guys!
Why would a girl post a lot of pictures of her with guys if she is talking to a guy?
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