Who was Caroline Olivia Zickerick's grandmother?

Context: Caroline Vreeland was born Caroline Olivia Zickerick in Washington, D.C. to Daisy Vreeland and Michael Zickerick. Her father, a German diplomat, served as the German Ambassador to Moldova and as the Director General of the German Institute Taipei in Taiwan. Her maternal great-grandmother was fashion editor Diana Vreeland. She is a grandniece of American diplomat Frederick Vreeland and a first cousin once removed of the Buddhist abbot Nicholas Vreeland. Vreeland spent four months of her childhood living at the German Embassy in Kingston, Jamaica while her father was stationed there. Her father later had an affair and her parents divorced. Vreeland's mother moved them to a Siddha Yoga ashram in Upstate New York. They left New York and moved in with her grandparents in Belvedere, Marin County in the San Francisco Bay Area. After graduating from high school she moved to Los Angeles to pursue a music career.

Answer: Caroline Olivia Zickerick grandmother's was fashion editor Diana Vreeland