This sounds more like Borderline Personality Disorder type of behavior than PTSD alone. Only a doctor or therapist who evaluated her can say for sure.
It's really good she is going to see a doctor, and it's probably going to take some time for her symptoms and behaviors to improve. Is she open to therapy?
The book "Stop Walking on Eggshells" is a great resource to help navigate situations like this.
When you are ready to leave, you can call a crisis line at any time and tell them of your concerns and fears and let them, the trained professionals, figure out what needs to be done, or not, to keep her safe and get her help. The more you can let go of it being your responsibility, and reach out for help navigating any self injury it auicidal behaviors, the more the proper professionals can step in. And hopefully the sooner she will accept that help.
In the meantime, any ways you can begin to set boundaries may help you eventually build up the courage to get of the relationship. You may feel bad and worried before, during, and after breaking up with her, and this sounds weird - but expect that to happen as part of the process of pulling away from someone who is in this place, and when it happens, don't take it as a sign you are doing the wrong thing, but just a sign that sometimes the right things to do are really hard.
If she texts you pictures of self injury to try to get you to stay, tell her you need her to stop sending them to you or you will block her number, and then actually carry it out if/when she pushes the boundary.
Right now, if you can't leave her for your well being, consider doing it for her. She is probably acting out in this relationship as part of her way of avoiding getting help and facing the pain she is in, The sooner she can't use this relationship and can't use you to try to regulate her deep pain, the sooner she will hopefully reach out to help to learn healthy ways to manage her pain and regulate her emotions. By staying with her, and not claiming your right to your own boundaries, it's possibly enabling her to stay stuck in this behavior. She may push back in boundaries, but you can keep claiming your voice. It's ok to say no, stop, enough. It's healthy - for BOTH of you - for you to own what you need and to set the boundaries that you need.