I don't want to hurt your feelings but in my opinion she's playing a game of some sort, maybe unintentionally/unconsciously. She won't break up with the BF after all these months yet knows that your feelings are stronger than "just friends"?
Your potentially hurt feelings should be more important to you than her feelings, at this point, in my opinion, and I think you should take a "time-out" from the relationship. That sounds cold-hearted and selfish but I do think, from what you're saying, that this situation isn't going to go anywhere good for you. Maybe in the future you really can "just be friends" but I think right now you're headed down the highway of hurt.
Good luck with this, and sorry to give you such "bummer" advice.
