I think being nervous about it is natural. There are lots of people in the world who are insensitive about disability and illness, and of course you don't want to be lumped into that category. But if you go into the interview with a genuine interest in learning from the person about her experience I think you will be fine. In fact, there is a student group on the campus where I work called DAJA, "Dont assume, just ask" which is about this very thing. They would very much prefer that people ask them about their various disabilities versus assume something about them. So if you are genuinely open and curious and you convey that without prejudice or assumptions, I think you will have a great interview. And I don't think you need to go in there knowing too much about the disorder. What you don't know, she can tell you. Just admit what level of knowledge you are starting from, and ask questions.

Good luck.

gg