First, it's essential that you grow some balls. Second, you need to delete her number from your phone, and throw out all her crap, or burn it. You need to cut off all contact from this girl permanently. A FB relationship is out of question, you're obviously still attached to her emotionally, and it's completely f*cked your judgement.
I may be coming across as harsh here, but I've been in a very similar situation as you and it's one of my biggest regrets that didn't take the advice I've given you. You don't yet seem to be comprehending how bad this girl has disrespected you, and she will not change. You didn't mention how old you are, but it's time to chalk this up as a learning experience and move on with your life. I guarantee you'll look back on this a few years from now and be glad you did.