Did i make a mistake?

so theres this girl i like for 2 years. we decided to be just friends (nother story :P) anyway. m best friend for 4 years got pissed at me for just talking to her, hes been an *** to me and to her, he flipped out while fighting with her over FB and stopped talking to me, i just replaced my best friends place for this girl i like, did i make a mistake? i hear you should NEVER replace a friend with a girl.