On the deepest level, this has nothing to do with your friend. It has to do with you and only you.

Why are you allowing yourself to be treated this way? Your best bet is to educate yourself regarding your issues. She has simply tapped into them for her own perverse reasons. Those reasons are her issues to deal with if she chooses to. You focusing on her issues is simply a way to ignore your own (she's got issues, not me).

There is nothing you can do about her. You are in charge and responsible only for yourself. Read books, watch youtube videos, talk to a therapist.
To repeat, this isn't about her, it's about you.
Your biggest clue is she has "normal" relationships with other people in her life. You are her target. Why is that?

When you love and respect yourself, it radiates out. It is the greatest gift you can give yourself. Others pick up on it, and treat you accordingly.