plenty of motorcycles doing 300 mph at Bonneville (there's even a Triumph mc named after the place). Her posture isn't ideal I agree compared to drag and speed trials bikes https://youtu.be/3Cq-DfTTPFw
These motorcycle drivers are continuously exposed to wind pressure though, in her case she would be suddenly exposed to it which probably would be not unlike hitting a wall.
In addition, her bicycle is not aerodynamic and likely weighs between 20-30 lbs, whereas a race a race motorcycle is very aerodynamic and might weigh between 400-500 lbs.
I'm sure the rolling weight of the wheels would dramatically impact stability as well.
