Hi there Guessthisisme,
Welcome! I noticed you wrote "you didn't have it as bad as some people growing up". Personally I think that the effect our past has on us, is more important than how that past compares to other people's pasts. So like you, I agree that comparisons aren't helpful. Better to just work on ourselves moving forward, in my mind.
When I retired from my career, I knew it would leave a big gap in my life, so my exit strategy was to move into a new job and a new line of work, which was working in a women's shelter. We had many skilled people there, and one was a person who's sole job it was to work with children who witnessed abuse. Witnessing your parent's physically fighting was a form of abuse. This is traumatic for a child.
She loves to tell me I must be “so broken inside to find satisfaction in hurting the ones she cares about”.
So you know she's really talking about herself here right, and how she has hurt you? But she can't handle those feelings, or accept responsibility, so she dumps that on you by accusing you of the very thing she is feeling? Confronting her with that would be fatal, and escalate the horrible things she says to you, and make the situation so much worse than it already is. In my case, I find it helpful to just understand it. I had a therapist once who suggested I use visualization to separate the person from the disease. So when my mom says stuff like that, I picture the disease monster (which for me is a deformed brain). It helps me not take is so personally.
I realized I needed to draw boundaries now, instead of when it would be too messy.
This is logical thinking. Good for you!
I do want to have a relationship with her eventually, but I don’t think she’ll ever be able to overcome her issues to hear me out.
I think you are right. Since coming to understand BPD, and accepting that my mom has it, I have also accepted that I can't change her. So I stopped trying. "Hearing you out" would be trying to "change her" in a way that she can't be changed. What I focussed on instead, was what
I needed to do/learn/change to navigate my relationship with her. I
radically accepted her as she is, and instead focussed on what I could control, which was how I communicate with her, and how I react to her. It hasn't been easy, but it has helped me a lot.
It’s like she wanted me to stay 17 and dependent on her forever.
Yep. Sounds like enmeshment. Also sounds like her fear of abandonment. Visualize the disease again.
She keeps repeating how I’ll repent and regret all these decisions later in life
This is veiled emotional abuse which she's doing to manipulate you to have her own needs met.
It's awesome that you are receiving professional help, and are thriving.

Maybe I am just a cruel and selfish/spoiled daughter who sucks people dry and throws them away. Maybe I am all the awful and pathetic person she says I am.
She's just projecting her own horrible feelings onto you again, by accusing you of the things she feels bad about. You know inside that she shouldn't be saying these things to you. Picture that diseased brain again. Try to separate the disease from your mom.
Telling you that you will regret this, is HER feeling. She can own the regret. Just because she says it, doesn't make it a fact. Sounds like brainwashing. What you ARE doing, is working on healing yourself, becoming autonomous away from her, and becoming an independent thinker.

I'm happy for you that you feel you have made the right decision. As for feeling the guilt, that is something I believe we all have to learn to manage after being raised by our parent to feel their FOG.
https://www.bpdfamily.com/content/emotional-blackmail-fear-obligation-and-guilt-fogShe told me I was immature, but why would I argue with someone who can’t be wrong?
You are so right. Never argue. It will blow up. There are other better communication tools for managing a relationship with a pwBPD.
Sounds to me like you're moving forward.