What should i do plz how can she trust what could be a peado :/?

my friend tells me days ago she has a boyfriend but and then after a while she tells me he 17 ( my friend is 14 and im 13) and she meeting him in town and she asked will i go with her and i could yh sure no bother and then i go soo he 17 and she went yh and i went who uu know him some1 from down ur dads and she went facebook :S then i was like he could be any1 and she was like no he's not he even rang me and i rang him :/// It still could be a perv ?? her brother (who is a even better friend of mine) he's 15 and he like he sound but me and his friends were talkin and were very weary but how do we talk her out of it cozz lets be honest it could be any1 :(dno what 2 do i dont wanna go and my really really goood friend (who doesnt like this girl ) is like im warning you dont go he could yahs and aperently he bringing a friend and there like 2 girls 2 peados 2 s ://// i really dont know what 2 do :O