I am sorry that you have to deal with all of this. Unfortunately this is an experience that many of us have had. It is very hurtful and hard to understand why someone who is supposed to care about you would do such a thing. Life is too short to have to deal with people like this.
I think you made a good decision to no longer be friends with her. She doesn't deserve to have you for a friend.
She didn't live with you and your ex so she really has no idea what life was like for you. She has no right to say anything to your ex about your life now. Did she honestly think that you would not move on and find someone else?
Try not to worry about her and stress over her. I know that is difficult to do right now but it will get easier. Your life is moving forward in a positive way. Maybe she is jealous.