What is she afraid of? Cooties?
Sorry to make light of the situation but it seems to me that she's overreacting just a bit. Why is it such a big deal. You changed the part of the bedding that came into contact with the person in question. Is this really what she's upset about? From what you've said and not really knowing either of you or the whole situation it sounds to me like there is something else that's bothering her and this was just the easiest thing to latch on to and freak out about. I think that you and her have some more talking to do and figuring out just how comfortable she is with this situation before it goes any further...