I had my lesson yesterday, and played two of my three pieces significantly better than I had last week, though not as well as when I practiced the day before. The third piece, the one I'd played really well the week before was just a little less well played.
But, Strings says I can start on Book 3, and started teaching me about the structure of the piece (which is important) and how the dynamics and such worked.
She also gave me a sort of overview of Book 3, which I think is helpful.
The random practice over the past week really helped!
My new piece (the first in Book 3) is a Gavotte by Padre Giovanni Battista Martini. Here's what the first page looks like: