If you went into more detail about your guy's history, it might be easier to understand.
When you are friends with somebody for a very long time, you tend to fall into the friend zone the longer you are friendz. It's certainly possible to be best friends and then move it into a relationship but it's not very likely. It took some balls to tell her how you felt, I don't see anything about how she reacted? It doesn't sound good if you think your friendship is over. If you guys are really good friends though, whether this turns into a relationship or returns to your friendship, it shouldn't be something you both can't overcome, although it seems hard to see that right now. I'm sure she's probably suspected it and it didn't come as a terrible shock. As long as she's honest about how she feels, be it liking you too or not seeing you that way, everything is going to be alright.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.