Helpless in Helping a Friend in a Toxic Relationship

I have recently gotten out a toxic relationship with a parent who was narcissistic, had a short temper, and apparently bipolar disorder (which they refused treatment for). After years of relief I hear from one of my dearest friends that they are going through the same thing. They’re parent got mad at them for who knows what and it’s to the point where they need the other around sometimes in order to settle things. The worst part is I have no idea how to help them because I was completely helpless until I was able to escape. It killing me that I can’t help them at all even though I know exactly how to help them. And for those who might suggest telling them how I escaped, I got lucky and they died of natural causes so I have no clue on how to get them out. Any ideas?