As Alainaluvsu says, this girl has some serious issues.
It seems likely that she would have behaved in this way with you whatever the reason, ie, if you were not in the process of changing.
She clearly has an attraction to you, yet is incapable of making committment. She wants, whatever it is she gets from you while lacking the personal maturity to give anything back.
She is definatley one to avoid.
As for her poison tongue, ignore it. There really isn' much else you can do.
If she does try to pester you in person the police may be necessary. I'm pretty sure they will support you. These situations are not as uncommon as you might think and they are trained to deal with them.
As for your father, many of us know that. Not that that makes it any easier. We're suppose to be able to rely upon family, yet for many people, family are the worst of our problems.
But again, if it hadn't been for this issue, I tend to believe that he would have done this for some other reason.
Sorry I can't be more positive. Like many people, you are just going to have to walk away.