Merv, if I'd been happy enough to send her up in one for all those hours while she gained appropriate training from an instructor that I trusted then I see no reason why I wouldn't allow her to continue. If her instructor said she was ready, then I would trust that she ready.
I seem to recall my instructor nagging me: "Where would you put it down if the engine failed now?" He would pull the throttle on the way to the training area, on the way back from the training area, in the training area, on the turn downwind, 200ft in the air after takeoff etc, etc. But after what seemed like hundreds of hours he decided I was safe enough to go solo even with what must have been a very unreliable engine in that C150. I imagine you do the same to your poor students.
Did you ever say to them: "You're ready to go solo but but not in the Jabiru we've been training in, it's just not safe?"