Complicated question about my boyfriend and my best friend? Please help!?

What your friend has too remember is that he likes you, he chose YOU and that it is YOUR relationship with him and no amount of tagging along on dates is going to change that! Tell her that you know how she must feel about the situation but she needs to understand that there is a line that she has unfortunately crossed. She needs to back off and leave you and your boyfriend alone, if i was your boyfriend i would be pretty pissed too!! He might get to annoyed and decide to call of the relationship as he knows that you are too nice to let your friend down. I know this is hard for you but i have been in a similar situation and my friend saw sense and backed off, and if she doesn't support your decisions then she is definitely not a friend to keep! Hope this helps and good luck x