Sounds really tough. And agonizing to anticipate. I'm so sorry. I can see how the worry of what may happen and that you might shut down would be really really hard to even show up.

If you feel like a part of you needs to talk about it, perhaps she will be able to help that part of you figure out some way of at least starting. Her desire to talk about it should be way less of a factor. She needs to do what is best for you, not her. If she senses that you are having such difficulty it would seem clear that pushing you is not the way to go.

I can only go from my own experience though and trying to piece together yours. My therapist would allow me space, even silence, if that is what seems safest. There have been times when he has asked and gone beyond where I could go, so I have shut down. He just then attended to that and realized that he had made a mistake. He owned it as his mistake not my problem. And worked to make me feel safer so that I could open up again.