My man is off limits?

ok at this party while i was dancing wit my friends my boyfriend is off with his so called best friend girlfriend "keeping her company " while her man is gone talkin to some friends but after the party we're talking him and his other homeboy have 2 talk 2 me so they say that the girl wants my man and keep her man this made me mad and he doesn;t want her and i trust him but the girl is my friend so why would she want my man what should i do slap her or talk it out