Dog biscuit,
You are going through a lot right now, I'm sorry that you are hurting. You are asking great questions and digging deep, I commend you for your courage to look at your issues, because it can be very difficult.
You are definitely not alone in your feelings, I can relate to the withdrawal that you are speaking about. I do that, too, when I am very hurt, and I understand when you say "What's the point?" because I think the same. "I'm going to have to deal with my pain alone, as always, so why try to find understanding from anyone else? They won't be there for me, anyway." (just a little taste of my mind chatter)
It's very normal to feel afraid of standing up for yourself – you might "lose" more people, and that is scary for anyone. I think it's important for you to express your feelings to your friends and loved ones. There are ways to do it without being offensive, if that is what you are worried about. If it were me, I'd wait until I felt a little more balanced in my emotions, if possible. I like to write it out, too.
Dog biscuit, are you able to let the feelings move through you without getting stuck in blame and stinking thinking? I try to focus on bodily sensations and not so much on the mind chatter. It's a real challenge, but it helps. Also, vigorous physical exercise helps me a lot, too.
It you'd like to express your feelings in writing, we're here! Write it out, say what you want to say to your friend here, and we will listen. Then maybe you'll feel more comfortable talking to her in person.
When you are ready to speak to your friend about your feelings, we have lots of tools here to help, like:
https://bpdfamily.com/message_board/index.php?topic=160566.0Keep writing, Dog biscuit. We're here for you.