I hold best friendship as a sanctity like marriage. (Not that marriages are that greats now-a-days rolleyes )
Your best friend comes above all. And thats not to say you shouldnt worry about yourself, because if you're real best friends your bf will want to to be extremely happy and successful and always stand besides you. If your best friend is really upset you should want to do everything you can to help ease that. HOWEVER your best friend should also understand that you want other friends, and help you with that.
Have a talk with her and see why she wont give them a chance. Let her know you really have fun with them but you want her to have fun with you. If she refuses to give them a chance and tries to make you feel guilty then she's not a good best friend. However if she has a good reason for not liking them, like they make fun of her sometimes, or are mean to her, you should stay with your bf. Why on earth would you want to be friends with someone who treats your best friend badly?