This might sound crule,
As we all went through the same experiance some time along our childhood.
Simply take the bended support off, and tell her to try to drive the Bike with out it till you can manage to find a way to fix it.
it will help her alot to experiance the balance, and she might be on her way to have the other taken off.
Just a suggestion not more.
I not: Try Toys R Us