I totally agree that you need to find a way to communicate that is comfortable for her. Journaling? Email? A chat program? You could describe a scene to her and give her a checklist, like the bdsm checklist but more specific to the scene, and get very short responses. Eventually, maybe she could be persuaded to share a fantasy of hers, with the understanding that it is a fantasy and that no one is planning to enact it. Whatever it is, praise her and be positive that it's a really great one. I will tell you from personal experience, nothing makes you feel worse than sharing a fantasy and getting a tepid response. Also, praise her after a scene. Let her know that you know it's hard for her and you love how well she's doing.

One final thought - give her two words, one that means I like this I want more, and one that means back off. Tell her she has to use each of them at least once in a scene. Praise her. Good luck.