My parents don't like my best friend!?

i have been best friends with this girl who i lovee soo much. we have been through thick and thin together ive been there for her always and i hoped for it to stay that wayyy. i mean so much to her and shes the same for me. but my parents have never liked her since day1 they say shes sneaky and a liar and a bad influence on me. but i still hung out with her on and off because of my parents forbidding me to hang out with her then letting me again. but now she is involved with this kid who is into bad "things" and is a bad influence on her. but i was hanging out with both of them then he got into trouble and my parents found out and now i cannot hang out with him or my best friend because they are both bad influences which yes i know he is but my friend really isnt she just hangs out with people who are but she has no bad influences on me and i know this for sure that she would never push me to do something i wouldnt want to do. my parents are forbidding me to see her again .. no communication at all the reason.. she hangs out with the wrong crowd and is together with someone who deals drugs who has been caught before. idk what to do she needs to change and get her act together because these people and her bf will only get her into trouble?? but how do i explain all of this to her to make her change she is happy being with him and thats how i want her to be but not with some one like him.. and all of her friends are friends with him so idk how she can stay away from all of these people idk i need help i want my parents to except her but they refuse too and im not happy without her she is my bestfriend and i love her i just want my parents to be happy along with my friend and myself pleasee someone helpp mee thank youuu :)