How to stop bbf from the bad influence crew?

basicly my best friend has been asked 2 go with da kl or as evryone says bad crew i dont know wat to do im currently talking on the fone with her she is going 2 dem becuz they are open with her and friendly what she actually mean is they talk about haram (no religious things) like boys and doing bad things and while praying talkin! she get influenced really eaislly and i dont want her to end up in the bad crew i am also afraid of loosing her 1 or 2 ppl who have went there r now rude arrongant dont care bout studies and negative ppl and 1 of them was actually top of the class and goody 2 shoes i desprently want to get her out i just dont know wat to say she says that she wont forget bout me and that she wont get influenced but im not takin her word for it once some1 in our class told her i sed somefin she believed it and stop talkin 2 me for 3days! she is gullible she says she will still be my best friend but its just i care bout her and i dont want her gettin hurt plzz help! :( btw i have another close friend who is close with both of us!