Ladies i need help !!! closure...it ended bad?

A girl i liked got to know me, we were in love, she was happy, i was happy, i wasnt sure and neither was she, i tole her how i felt, and she with drew and then started seeing my best friend behind my back. i found out but haven't told him or her. i cant stand to see them i fill up with anger from their betrayal, i need help to get over her, i cant help it but i do want to get revenge on her too, to at least show i was wronged. i need to know what ill hurt her or at least get her attention to let her see its not the end of my world