Well, if your date doesn't ask you why you're not drinking, you can tell her a white lie and say that you're just not that much of a drinker. Or better yet, oh, well since I drove here, I better not indulge. It's better to be safe than sorry.

Whatever you do, do not tell her anything about your mental issues as that will scare off most people, including people who already know you. Trust me on that. You seem to be aware of that already. Only tell people that really need to know those things like your Dr. or after you've known someone for a long time and feel like they won't head for the hills once you disclose that information.

If she asks you any nosy questions, then just change the subject right away. A good way to divert the topic is to ask her about herself as most people love to talk about themselves. As for family and friends, do the same thing. Lie about being on a diet or whatever, or that you have to get up early the next day and that you won't be able to deal with a hangover with some important thing that you have to deal with the next day at work, etc....

Good luck with everything.