Who is Zada Landau-Banks from The Disreputable History of Frankie Landau-Banks and what is their importance?

Zada is Frankie's older sister. She recently graduated from Alabaster Academy and has since started college. During Frankie's freshman year, Zada took him under her wing. She is a source of advice and familial support whenever needed. Zada has a much closer relationship with Frankie than anyone else in their family.