I write without a plan. A friend once asked me if I wrote with the front of my brain, and I said, "No, I write by the seat of my pants." But I have known for years that Vicki and SarahBeth would end up where they are (well, SarahBeth isn't quite in her position yet, but she will be very soon), even when I didn't know how they'd get there.

And The Diamond Age, by Neal Stephenson, was a big influence on how I saw this, and I've now added it to the Ten Pillars of Modern Literature (it is the tenth entry, in fact, but this is not to say that there won't be more entries at some point).

However, since this is a bit of a spoiler, I urge you to get and read The Diamond Age first (unless you already have), and then read my comment about it.