Girlfriends parents :(?

im 15 i went to my gfs cuzin party he had just got back from the army.... he offered me a beer i said no. then he said come here so i followed him inside and he threw me 3 jell-o shooters...after he walked back outside i put em back cuz im not gonna have any alcohol with her parents there u no....billy told his aunt he gave me the shooters then his aunt told brandys mom now her mom thinks i was drinkin and ****.....i put them back but every1 thinks i drank them how do i get her parents to believe me i mean i love this girl weve been together for a wile and i dnt want anything messin it up wht do i do