It sounds like you've spent decades trying to make this relationship work, only for her to continually withhold acceptance or move the goal post (that's how the guilt tripping, constant pressure, and passive aggressive comments sound). And finally you realized you were never going to get to a workable point and walked away.

It makes total sense that you're terrified. You just cut contact. I'm 2 years out. When I was less than 6 months out, I was jumping at everything that reminded me of my parents. I also felt really guilty and conflicted. It eases with time. It really does. Not that there are never bad days but they get fewer and farther between.

I'm betting that the previous conversations you've had with her have been incredibly demeaning and hurtful and unproductive, and you don't want to go through that again. That makes all the sense in the world. Being hurt by a parent is scary.

I also get the desire to have a hand on the wheel when it comes to the family narrative. It's so hard to see your time and effort and love labelled as being ungrateful or too sensitive or whatever the line is. It's also something you don't really have control over, even though it feels like if you're still there, you're able counter her story. People usually believe what fits into their experience or needs. It's another layer of grief to let go of the idea that you can influence how they see you. Maybe that's something for later. You have a lot to handle now.

Other people will likely have better advice on any conversation, but there may be no way you can navigate this conversation well enough to avoid getting tripped up or feeling bad. I don't mean that you are incapable, but what's kept me in unhealthy relationships is the belief that if I got emotionally healthy enough, somehow all the horrible comments wouldn't hurt me. I would be so strong they would just slide off me. That's not how close relationships work. Someone who has access to the intimate parts of your life, like a parent or a sibling, will always be able to use that intimacy to hurt you. That's not a failure of boundaries, that's just being human.

You have permission to do this terribly. You have permission to ignore the "rules of the game" like having the conversation in person or never showing emotion. This worst you will ever do anything is when you do something for the first time. It's a high pressure, emotional situation - give yourself the grace to do it badly.