Who is Viva from Caramelo, or, Puro Cuento: A Novel and what is their importance?

Viva is Celaya's best friend. She is a couple years older than Celaya and a bad influence on her. However, she is the only female influence that Celaya has. Viva's parents are very kind to her, always asking her what she wants and what she needs. Celaya both admires her and is jealous of her. Viva also encourages Celaya to move out on her own and be different than every other Mexican girl.