Man, STL, that's a lot to deal with at one time. I'm sorry you're going through all of that.
You need to remember though that it's not your fault and you being there is a very nice thing for someone to do for a person they only had a fling with. It does sound like she's leaning on you quite a bit. Has she sought any counselling? I think that talking with a professional after such a traumatic event would be a good idea. That might give her some tools to help deal with what has happened and also give you some relief. It's certainly not easy trying to provide that kind of support.
If you ever need to vent, I'm available. It's certainly helped me in the past.
For now, just take one day at a time and remember to take some time for yourself!