Ugh I don't think I have any great advice for this but I can sympathize just from going through something similar right now. I also have a friend who's going through a thing right now (not to this extent) but she's definitely lashing out at friends in a similar fashion. It's draining to deal with and such a mine field to navigate because you wanna help your friend for dealing with issues that they are now kinda putting you through themselves.

Like I said I'm not sure if I have great advice for this. I'd maybe suggest getting yourself some therapy if you have access to it just to keep your headspace in shape, and if you can, strongly encourage your friend to do the same for herself because she 100% needs it. Like you said, you guys aren't counselors, and while you can be great support, it's really not your job or area of expertise to really help her on. That suggestion could go extremely right, extremely wrong, or anywhere in between, but if she's asking you for advice anyway, that could work as your opening. Even if she doesn't take well to the idea, I'd still keep pushing it when you can because that's honestly the best way you can support her right now without sacrificing your wellbeing just to accomodate her poor coping mechanisms.

I'm afraid that's about as much as you can do between this and what you've already tried. People only change when they are ready to, so I'm sorry to say there's no secret thing you can do to turn a person's life around and change their demeanor. The best thing you can do is just be welcoming and encouraging when you see someone taking the right steps and hope it sticks with them.

Please take care of yourself in the meantime though. Going through a bad experience doesn't excuse someone from hurting other people, if you feel bad don't take it lightly because the other person had it worse. That frustration is what keeps feeding that behavior. Take a step back if that's what it really takes.