how to get through to her? i really need the MCRmys help!

alright this may be a long one so bear with me. so my bestfriend and her "bf" have broken up and gotten back together like 7 times and im tired of it. the latest was on wednesday. they were goin out for 5 months and he just broke up with her no actually wait he didnt have the balls to break up with her so he had to make his friend do it. oh but thats not the worst part. while his friend was breaking up with her he and his other friend were laughing at her. yeah thats right. she was about to cry and he was FUCKING LAUGHING! this was all on the bus so after everybody else got off i screamed at him. shes my bestfriend so of course i was gonna yell at him. i mean come on? laughing? RETARDED! ok so a couple hours later she texted me saying "were goin back out" so of course i was freaking PISSED. i mean seriously? hes a jackass to her. not jus by laughin at her. he ignores her all the time except when theyre alone. but otherwise hes just a dick. anyway. so by now im pretty tired of her goin back out with her. she always chooses him over me. and she said the only reason he was laughing at her was to "fit in" i say thats bullshit and hes just a douche. i hate him more then ive ever hated any other person. and the only time weve ever had another fight was in the summer. because of him. the same reason. he was being a dick to her. how do i convince her he is a piece of shit? ive tryied oh ive definatley tried telling her. but she always makes up exscuses. im just tired of it. im tired of him. im tired of being put after him. ever heard of chicks before dicks? seriously? kay so could you guys help me? it would mean the world. i just really want my bestfriend back.