Why some girls fake flirting just to reject the guy?

I met this girl twice accidentally but I noticed she's one of the girls that fake flirting just to make the guy take a step and talk her then she reject him in cold way usually. I have been there before with time I avoid these type of girls
Why some girls do it? Are they broken? Desperate? Mental issues? Or other Things?
Why some girls fake flirting just to reject the guy?
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