You were more that just a friend.
Then everything changed, and you became a brother...
But as everyone always sed, a boy and a girl can never be "only" friends.
Everything really changed when the girl started to *loose* feelings about him.. He started to think the girl was madly in-love with him, but he was wrong.
He broke her in to peaces thinking it would be the best way to avoid feelings. He made a lot of pain that she couldn't support. It brought her down...
Now the only thing she regrets the most was to ever thought that someone who broke her heart once... Won't do it again.