I've had my 4,6 and 8 year olds with me in planes and helicopters.
I'd suggest that as soon as you get out of the circuit, with forewarning, you execute some turns and examples of the maximum manouvers you'll be pulling enroute, then if she hates it you can quickly return to the field.
I generally explain what I'm going to do to passengers, then bank the helicopter fairly steeply both ways, if they're fine with that then they'll love the whole trip, if they don't like it then see if you can fly at rates that they can accept.
In a fixed wing I try to avoid pushovers, unless they want to experience the butterflies! That's a sure way of having Billy Barfa turn up unexpectedly on the scene to ruin your day.
More than likely she'll fall asleep within 15 mins of takeoff anyhow and not wake until after you've landed.