Some suggestions:

Take care of yourself first. Fully. You get to set boundaries, you get to say No, you get to even walk away from this person. You get to tell her that you no longer want to hear it.

Keep your focus on how you are feeling when possible. You are feeling overwhelmed, pay attention to this.

You don't need to pay for her trauma, you are not her therapist, you are not in a co-counsel type relationship with her. I even want to put the word -Boundaries- in bright red and caps cause they are so important.

What happens when you try to redirect the friendship? Like if you suggest that the focus be on fun things, a walk through park, a mutual interest that is not about mental health issues?

I have PTSD, but I am more than just that. I am responsible for my actions. I won't make friendships all about my PTSD, because that does not work for me. It would make me too vulnerable, too triggered, too unsafe. And it would also be sorta gooping all over my friend. For me, it would make boundaries all loose and nonexistent.

My number #1 thought on this is to underline my suggestion that you focus on yourself first. Your own needs and wants and desires. That you remember to say No when you need to. That you take yourself out of overwhelming situations when possible. That you be a really good friend to yourself first.

Sarah