Is it possible for a girl (who is my best friend) who only likes me as a friend to fall for me later on?

Well, actually, it could happen, just have faith and maybe it will happen someday, I'm kinda going through the same thing, only my problem is kinda worse, but I haven't given up hope and neither should you! Keep on doing what you're doing and, I'm not kidding when I say this, pray to God and He will guide you.