You have some choices, the way I see it. You can either accept her for her "selfishness" or whatever you want to call it, or you can just choose to not be her friend. But you have to remember, that she might have actually been that busy, I know that when I am too focused I don't pay attention much to anything else and reply to someone like your friend did and have had fights happen before, but they realized that's just how I am! I hope this helps!
