Heh, and here I was, on the other side of the coin thinking you should just say sure, and go out with her to have fun. I went on many a date (in the short 5 months between coming home from the mission and meeting the girl of my dreams) with girls I wasn't really in to, just to have fun, make friends and test the waters.
So, unless she is totally psycho, I would say go out, have fun. Since I know you, I'm not worried you would do things that might suggest more of a relationship.