Girl gives IOI and then rejects you?

Please help me understand this.

Why would a girl lead you and other people(when you tell them what she was doing) to believe she is definitely into you and then look shocked when you ask her to dinner and give a half-hearted excuse to reject you.

Even girls I talked to said the girl had to be interested.

Thanks

Updates
+1 y
Title should read IOI's. There were several... I was *really* sure lol
Girl gives IOI and then rejects you?
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