If she is smart, she will first get her grandfather to not pay x amount but to agree to pay whatever he feels it is worth, even if he feels it is worth 0. Then unveil the grandmother scuplure cornering him to pay a high price.
She should also let the craftsman bring it, and give him ALL the money or at least the majority. When the craftsman will say something like it is too much, she would reply that it isnt too much since she is investing in him. And tell him his talent is worth just that much.
This way she will earn lots of brownie points, show she can corner the grandfather and pick out and see the value of talent