Yes, 12 hours is way too much. It is mentally, physically, totally exhausting.
If you get the chance, work with her on three things, very slow straight line riding while slipping the clutch (friction zone), very slow and tight circles and esses while slipping the clutch, and two wheel braking to short stops. Of course work up to these...bigger circles, slow big circles, slow smaller circles, slow really small circles, etc.
It's not what you look at that matters, it's what you see.
Henry David Thoreau