Hi fefa,
Both of my adult step daughters likely have personality disorders, one probably BPD, the other maybe anti social? Like you, I have done and said things to them, and then they want some sort of apology from me. The younger one doesn't even want an apology, she just wants me out of her Dad's life (Dad was her 'person'). This is really really tough, I get it.
Something I am learning to do in the two years since the stuff really "hit the fan" is to disconnect, as Pursuing Joy explains. You need to focus on you and the life you had before your kids. I know it sounds really hard to do, and believe me it is.
But this is not personal for you and it isn't for me either. I didn't raise either of my step daughters, they were adults when I met them. My husband and I have given $8000 dollars in cash to the oldest, helped get her car out of impound after a DUI arrest. We saw her and her kids every other weekend for a year as she was going through a rehabilitation program after (besides an extreme DUI) also getting arrested for possession of cocaine. She made it through that program because instead of hanging out with her friends, she had us. For financial, emotional and moral support. Then, 1 week after finishing her program, the oldest goes to another state with her boyfried of less than a week to take his then 2 yo kid from it's maternal grandparents. After they did that, she must have got her younger sister on her side, because then my youngest step daughter "disowned" her Dad because he wouldn't divorce me immediately after I unknowingly "stepped in it." What actually happend is I texted some stupid stuff about being careful because of COVID. Because my oldest step daughter was acting strange (this was before the sprint to another state to take a kid, it now makes sense why she was acting odd, I though maybe she was on drugs again) I also texted her ex husband, just to touch base and so he had my number. I had no idea what was actually going on in either one of their lives, how could I know? I am not on social media, I don't check up on either of them. I have a life!
I know now what's going on only because of going through all the stages of grief and getting marriage counseling with my husband. We went through hell the last two years. Also, due to the oldest going to get the kid with her new boyfriend (twice), the boyfriend got slapped with two expensive lawsuits. I would have advised my step daughter to Not get involved with this person, we are helping her financially! But I didn't do that, she never gave me the chance to. They are really lucky they were not arrested. All of this happened without my knowledge, but me just being "me" triggered them and they went into attack mode. Proactively went into attack mode. This is part of the disease.
The thing is you know Nothing about what's really going on in your kid's lives, let's face it, they have the internet and there are other influences besides us. Way bigger influences. And we thought we knew this kid, since we had cosigned on her apartment at the time. We helped her move, we thought she had no friends...we were wrong, we don't know her at all. Optimistically, we thought she was on the straight and narrow, being "good." We had no idea what she was really up to.
Don't take anything personal, try to get a relaxing hobby like gardening like PJ suggests (I also garden and so does my husband) focus on your life, who you want to be now sans worry and stress. If she does come back one day, you don't really know what that will even look like. Maybe it will be in more crisis. Maybe not, pray for her and hope for the best. That's all we can really do.
good luck, I hope you find some peace. You deserve it and you're a good person.

b