Finding out a bit more about PTSD when your friend says they have it is a very supportive thing to do. Trying to sweep in and be her knight in shining armour, chosing to be her carer (has she even been consulted?) and being there to 'protect' her from her decisions is not.
Very many PTSD sufferers have strong feelings of not being in control of their own lives at some point. Be it victims of violence where they have felt like their life hung completely on someone elses choices, be it victims of abuse where the closest people to them have manipulated and betrayed them in vile ways, be it natural disaters, accidents where the victim had no control over the outcome, be it veterans who saw their lives or others hanging by a thread.
As part of her recovery it will be essential that she can feel like she can set boundaries and have those respected. I know it's hard when you think someone is making a poor decision but the important thing is she needs to be free to make decisions (poor ones as well as good) about who she wants in her life at any point. She may well realise she reacted badly and decide to try to get close to you again, and at that point you can both mutually decide if that's ok. Untill then don't a) waste your time and b) keep showing her how little respect you have for her choices by continuing to try to contact her when she has said no.
At the end of the day forcing yourself (physically, socially, emotionally, psychologically - whatever) on someone who clearly is saying 'back off' is wrong. In fact, it verges on stalking.