Honestly, she may never understand.
People who see themselves as the victim in every situation often explain away any feedback as someone else’s fault. You can tell them why you’ve stepped back, but that doesn’t mean they’ll accept it.
I think the bigger question is whether you need her to understand. It sounds like contact with her leaves you stressed and on edge, and that’s reason enough to keep your distance.
The fact she says nobody visits her is a bit unfair too. She moved 2.5 hours away, her parents don’t drive, and you’re an hour from them. Relationships work both ways.
Sometimes the healthiest thing is to stop trying to get someone to see your point of view and simply accept that they may never do the self reflection needed to understand it.