In every CCW class I've held, around 200 students in total, where husband/wife, guy/girlfriend attended, I hear the same reaction when I say the words, "Guy's, because you shoot a large caliber gun there's no reason to assume she will be comfortable with it". The girls all chime in with "See even he says I'm right".
I would never have a new-be, male or female shoot anything over a 9MM for the first box of ammo. If they have never held a gun before your creating unnecessary problems. Flinching is the biggest issue to undo.
This isn't a sexist statement. Women, new to guns are tenative, fearful and scared, more-so than those males I've taught. I learned quickly that respecting those issues goes a long way to getting them comfortable with what happens when the trigger breaks.
To the OP. I believe the guy next to you was trying to show as others have mentioned, what a "real" kick would be like. You did well in blowing him off although I would have explained to him the first time why more isn't better in this situation and that you were not comfortable going there with this student.
Three hours of range-time is pushing it. I'm quite sure she had a very sore wrist when she got home. After the first complaint about her discomfort I would have stopped and dropped down to something smaller. The second complaint she gave you was your signal to stop and re-think what were your (Vs Her) priorities.
Just my ol 2¢