Most Helpful Girl
I think you should mention it at least in conversation. That would weed out people who think it's an issue and save your time as well as hers. Of course it can be tricky working it into the conversation. I doubt you wanna start a conversation with "I don't have all my fingers, you're free to run away now". Although, if I was in your position, self-deprecating humor might be the way I'd go about it. You should do it in a way that you're comfortable with. Once you've mentioned it, you don't have to discuss it further if you don't want to.