Answer: marching to her own drummer
Explanation: According to Ellen Winner's book , marching on your own drummer is described as doing things or task according to you own way and it does not consider other social norms or people. Ellen describes this as the ability to perform or do tasks that are above children's standard and age which is regarded as creative or artistic gift .
The act of Linda in the question states even being of 12 years old , she has the ability to create sculptures accordingly on her own without the help of instructor whereas other student takes the guidance of instructor. She is marching to her own drummer according to the Ellen's concept.