Indeed, she would have hit the power floor of the Vortex on the big ring at 60 watts in all of the reasonable rear gears. It’s really sensitive to flywheel speed.
My recommendation for that specific trainer would be to do workouts in the big ring and whatever gear in the rear that makes the chain not angle much.
That should remove the power ceiling for anything but all out sprints and improve the road feel (the flywheel is very small so spinning it faster smooths things out).
The downside there being that recovery intervals will need a gear shift to avoid the power floor. The trainer does get somewhat loud when spinning fast.
However, it’s a good trainer for the money IMO and I did not regret the purchase. It’s now a dedicated trainer for my wife’s bike.