(I don't own this picture. All Rights go to the owners.)

Name: Nova Starlight
Age: Adult
Gender: Female
Species: Mermaid
Appearance: Long purple hair with light blue hairstreaks in low pigtails, light brown color eyes, light purple skin, a light purple mermaid tail and wears a white short puff sleeve shirt, a navy-blue skirt tied around her waist, light blue teardrop earrings, light blue and light purple striped armwarmers, a light purple and yellow striped satchel, a light purple vest and a light blue teardrop pendant.
Mermaid Popstar: A light blue long sleeve shirt, a light purple skirt tied around her waist, white butterfly earrings, light blue and white lace fingerless gloves and a white butterfly pendant.
Personality: Kind, smart, caring, talented, brave, strong, creative, helpful, free spirited
Crush: SpongeBob (Crush later Boyfriend)
Friends: Patrick, Sandy, Squidward (Sometimes), Mr Krabs, Karen, Kelly Daughter of Plankton and Karen
Enemies: Plankton, Squidward (Sometimes)
Family: Aqua (Younger Twin Sister)
Others: Works part-time at the Krusty Krab as a waitress and works as a Mermaid Popstar with her younger twin sister Aqua.

Sounds like Mandy Moore