Try to do the 3rd person view of looking for inflatuation (like looking for signs like staring, etc). Or, if you and your boyfriend are on solid terms, ask your friend. If she is your best friend, she won't be (too) offended by this. If you find that you friend is crushing, don't try to destroy it. Love/inflatuation is a state which can potentially destroy the bearer, so just let it be. There is not much you can do at this stage, but as long as your boyfriend stays with you, your friend will eventually move on.
A thory goes that love is a sign of maturity. As far as I'm concerned, teenage love is a bit overated, and is probably just a strain of inflatuation.