Most Helpful Girl
This is a difficult question to answer. Not because the question or situation is difficult, but because I knew what happened between you and her all this while.
Firstly, sorry to hear what happened. I empathize, and I understand how you feel. However, I did warn you not to put too much into this before, and that her actions did not suggest anything more than that. Remember you told me before that you were very sure she liked you, so did your parents said so. But the actions which you've described in most of your questions were inconclusive as to whether she likes you more than a friend.
To really answer your question, we wouldn't know for sure why she didn't choose you. Maybe she liked another guy all along, or maybe she didn't connect with you romantically. It's not your fault, neither is hers. Regardless, what's done is done. Don't get too disheartened and allow your heart to heal for a while. Hopefully you learn something from this, take it slow with the next girl you like.