I know it's been a while but I thought I'd come back and post a followup.
So, as mentioned above, I got my courage up and asked for a second date. We made plans for dinner that weekend and after a short, playful exchange, I left her alone. I figured there was no point in pushing my luck and seeming "too interested" once the date had been made. I was doing everything right as far as I could tell, just going about my business, not paying any special attention to her. In fact, I didn't even log on to FB at all on the day before our date. But the morning came and there was a message from her, cancelling our dinner. This wasn't totally unexpected because of some issues with her schedule that I was already aware of, but her cancellation did not include an offer to reschedule. We all know what that means.
That was over a week ago and we've had very minimal interaction since. All signs indicate that my chance with her has come and gone. I'm sad about it - after all, I've had a crush on her for a long time and her interest level was high for a little while, and I'll never really know for sure why things turned out the way they did. But this has been a learning experience and a wake-up call for me. If another "golden opportunity" ever presents itself, whether it's with her or someone else, I'll be ready for it.