How the heck do you peel someone off of you that is tring to charm you back into their lair? My self respect is in the toilet so the compliments sound nice, but this sugar she's pouring out doesn't cover up the bitter taste she's left.
You focus on you. You keep your goal in sight. You begin to see more and more that what you have without her is better than what you could ever imagine, for a split second, of having with her (especially because you know it won't last). You do it because you know you must, at first, and as you heal and grow stronger, you do it because you WANT her gone. You do it because you never want to feel that way ever again. You do it because you LIKE feeling the wind in your sails, standing strong on two feet, having control of your own life, walking tall, etc.
See... .she can dump you, but when you dump her she can't handle that. My ex was the same way. Don't worry. If you stick to your guns the act will die down eventually. She will realize it won't work. She'll be desperate to get your attention. Mine would call me crying, or just call me in the middle of the night and say, "I'll love you forever." She smashed things I gave her over the years. But eventually it died down, and probably within a week or two she had another guy. Thankfully, by that point, although it hurt to hear her say "I'll love you forever", I knew that didn't matter. You can love someone you will not allow yourself to be with.
You can still love her... .from a distance. And love is not the same as "need". Love means you still care about her and what happens to her. I still feel that way about my ex, but I will never ever let her close to me ever again. Those walls are high and thick.
How can you tell her? I eventually just went the low-conflict route, meaning that I would say, "I'm sorry... .I love you. You are like an old friend. But I think we were just never right for each other." That sort of agreed with many of the things she had said over the years. It was less confrontational and triggering than, "You're nuts, and I cannot stand the abuse you put me through."
But being straight honest with her, without going into details, might be good, too. "I love you, but I'm sorry. I can't do this any more." I would, however, make it more about you than about her. I would add in, "I need to take time for myself and work on myself. I don't like who I am anymore." There is an article on the board somewhere that recommends how to break away from a relationship with a BPD person.
Have you read this? It has some good suggestions.
https://bpdfamily.com/bpdresources/nk_a110.htm