Who is Jinny from The Waves and what is their importance?

Jinny is an upper-class woman, who like Neville, has complete confidence in her identity and never questions anything she does. She is described as unapologetically superficial, and her love of color, clothes, and other material possessions make her popular throughout her life. Note, Jinny doesn't strive for popularity, but rather, expects it.

As Jinny gets older, she comes to realize that beauty is fleeting, and as a result, her thoughts turn back to the others. Surprisingly, she comes to relish old age. Her intention is to continue her wild social life right up to her death.