Which means, it is just sloppy and uninterest. And she is prodigy on the piano, so she can read music and do the motor coordination just fine.
I second what Aculady said.
And I would be very careful about assuming it's just careless or sloppy work. It may be-- but if there's an underlying problem, you don't want to be punishing a child for something that's not their fault.
Piano proficiency is very different from handwriting-- handwriting is not only a motor/planning issue but also needs the language centers of the brain, which are bypassed in piano.
DeeDee