Quads require rider input to stay level and to turn. That input requires an ass big enough to use as a counter weight. If she isn't physically big enough to pull in a clutch lever she doesn't have the ass to make it so the bike doesn't slam her to the ground. So right now she is on a smaller bike that doesn't keep up, well slow down the rides a little and let her figure out how to get around obstacles. Later on when she is physically big enough to actually ride a bigger bike she will be light years ahead.
Kelsey Foley ( Lil Osoto) was a great rider, On a 450 she could keep up on any fast ride no problem, Hell she would follow Pajama Guy off lips and razorbacks , Nobody in there right mind does that. She was a great rider......... Until that one day when the bike got out of shape and she needed another 40lbs of ass on the seat to keep it under control and the bike pile drived her into the face of Brawley Slide. It was two weeks of her sitting in a dark room before she could go back to school and it was another year at least before she was back to her normal self. It was also the last time she rode a quad.
That can happen to any of us at any time and the only way to actually prevent that is to stay home and not ride, but if she isn't physically large enough and strong enough to pull in the clutch, give her a fighting chance not to have it happen to her.