She is a mess. That's the honest truth of it. Imagine having to figure out all the cr@p she has to figure out? Why she went into crisis, facing the affair and STD, figuring out what she is going to take from the crisis and what she is going throw back. Then having to figure out how to face whatever it was she needs to face from her childhood. Its a whole lot. Not a cake walk.
So, she is looking to you to lead her out, gently, while still allowing her to figure it out.
The key for you is to keep to your path, but, remain open to the possibilities. She spooks when you move too close and panics when you move away. I know you feel like you are walking a tightrope.
But you are doing it. And its ok to take a time out, or remove yourself as long as you are doing it respectfully.