Why she mad at me?

She is my friends with benefits we both went at club yesterday she started flirting with other guy i thought she like him so i didn't disturbed her. i approach other girl n we talk n then we click n went for dance n we did make out n spend good time together i played with her boobs n my friend saw... and that girl left i text my friend let's go it's late now... she told me fuck off n left alone... i mean wtf?
Why she mad at me?
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