I also agree that it was a big accomplishment for you to go over to her house and spend some time. You should definitely pat yourself on the back for that and chalk it up as a success! it should give you another reason to believe that you can absolutely do more stuff like that. You succeeded, you didn't die in the process, and the world didn't come to an end. ;-) Yay!

That being said, I would work on my exit strategy. I know that for me, if I left somebody's like that, it would make me even more anxious wondering what she thinks or what would happen if I ever run into her again!

I would probably just send her a little message (maybe facebook) and apologize for taking off without saying goodbye. I know that if somebody took of like that on me I would be like, WTF? So, just send her a little note. No big deal.

The next time that you are out (with anyone) and you feel like you just need to leave. You could always just nonchalantly look at your watch or clock and say something like, "wow, it's already (whatever time o'clock). Time flies when you're having fun. I'm sorry, but I've gotta take off. But it was great seeing you! Maybe we can hang out again sometime soon?"---As you're talking, begin making your way out by grabbing your car keys, jacket, or just standing up moving toward the door.

By doing that, you'll get out pretty fast. To me it's a much more polite way of saying, we're done right now. I really need to go now. Thank you. Good-bye. :-)

Just my two cents, but I don't think you really need to get into a whole lot more than that with someone that you're just starting to meet or get to know. Just take one step at a time. If you begin to build a relationship with someone, say after hanging out a few times, then you can always discuss more personal stuff.