Revenge?? pleaseee read....?

okk so me and this guy were goin for a LONG time and one of my best friends[carly] liked him the whole time we were goin out... so time to time carly would go over to his house with my other friend [samantha] and hang out and they played truth or dare and both of them ended up kissing him... carly didnt tell me when it happend and he accually was the one that told me later. then i found out by samantha that after me and my bf broke up carly admitted that she likes him and is trying to keep it away from me! so samantha told me that on friday carly went to his house by herself and they hung out for a long time... wow this pisses me off soooo much! and i still like the guy even tho we are broken up and carly knows i still do... so what can i do to get her backk? pleasee helpp! =] thanks