I wouldn't lie, but I also wouldn't answer the question straight out. I'd dodge it. Examples
1. None that could measure up to you. (not sappy, but teasing)
2. Why, do you want to be my first?
3. Not nearly enough.
4. It's not important.
5. I'll tell you later.
6. Nice weather we're having, isn't it? How about those Bulls?
7. 134
My point is, that you're not obligated to answer any question. You can turn it into a joke, or you can simply not answer. After you know you've got her, then feel free to tell her. She's not going to leave because of that if she's gotten to know and like you. Girl have asked me several questions on dates that I didn't want to answer that early, and i did a couple of things. I made a joke, I answered part of the question, or I said with a smile that they weren't going to find out yet. Even when they realized that I didn't answer, we laughed about it and they let the subject go. As long as the question has no direct relevance to them, such as "are you married", no one's going to push too far.