Issues With A Best Friend....?

Look it is none of your business. You have expressed your feelings and concerns that is all that you can do. If you were a true friend, although you may not agree with her beliefs or life style you don't judge her and get mad at her because she is doing something that you don't agree with. You can let her know that you still care about her and will be there for her if she needs you, as I'm sure she would for you, but you should also let her know that you won't be around much if at all as long as this new guy is there because you don't feel comfortable nor do you like what she is doing.