During her 22 years at the Institut du Hobogirin of the Ecole Francaise d’Extreme-Orient in Kyoto, Seidel had become the centre of gravity for the many Western scholars of East Asian studies who ventured to the ancient Japanese capital to conduct research.
During the Nazi era, her father, who was an aviation engineer, stood by her mother, who was descendant of a distinguished German-Jewish family; they illegally sheltered a Jewish friend at their home throughout the Second World War, risking a death penalty.
After a brief marriage to the Bostonian scholar Holmes Welch [de], with whom she co-edited Facets of Taoism (1979), Seidel devoted her life completely to her scholarship and to the Hobogirin Institute.
She was an international scholar: German in her upbringing and cultural identity, French by citizenship and education, residing and working in Japan, and wooed by the English-speaking academic establishment.
Although Seidel did not undertake long-term systematic fieldwork on Chinese religion, she paid meticulous attention to contemporary religious phenomena, which she interpreted as a continuum with ancient textual traditions.