Was she practicing the Rachmaninov B minor Prelude cadenza in the opening few minutes? I couldn't be sure because she was breaking it up into tiny phrases.

The practicing seems efficient and, in this session at least, geared towards getting notes learned and in one's hands. What I like is that there's clear evidence that there's a mind behind everything going on.

Also, there's a clear feeling that she's a professional. She's taking her time. There's no rush in getting to the proper tempo, and she doesn't gloss over the easy parts. In the Franck sonata, like a lot of chamber literature, what's difficult for the piano isn't necessarily difficult for the soloist. A good musician works on all the notes, not just the hard ones.

Surely taking one's time, practising toward goals, are simply good practising and not exclusive to professionals. The thing that makes me think she is a professional is that she already has the skills as well as the piece so that she can brush through things relatively quickly, in a manner that seems relatively unstructured.

I didn't write "unstructured" - I wrote "relatively unstructured". I have done similar shortly before a recital when I knew the piece well, had the technique intact, and needed to go over and polish it. But as a student acquire skills and learning new pieces, I need something more structured than what I see there, because of the kinds of goals that I need to pursue. The idea I was expressing in my first post, I think, was that the form of practice responds to the context, or something like that.