this question is unexplainable (because sometimes love is so big that words is not enough to show what you feel). but if you ask her I'm sure she will say tons!
You tell her how you feel and what you think of the relationship. After you wait till your friend is done telling you how she feels think about her answer. After if you don't think shes going to stop...
why do i love my best friend so much.
possibly because you have been around him/her for a reasonably long time...if so then the attraction has basically gone into overdrive because you have realised...