[1][2] Sosenko is perhaps best known as the "formidable"[3] manager and writer for American cabaret singer and fashion celebrity Hildegarde,[4] for whom she wrote "Darling, Je Vous Aime Beaucoup" (1935).

[5] "Her ingenuity, her inventiveness, her organizational genius and her undying faith in her merchandise stamp Miss Sosenko as just about the smartest manager in show business today," declared journalist George Frazier, in a Life magazine profile of the pair in 1943.

[2] Sosenko produced The Raleigh Room (1945-1947), a radio program starring Hildegarde, with Alan Jay Lerner as head writer.

[11] Sosenko had a large collection of theatrical memorabilia,[12] and opened a small gallery in 1965,[13] selling and trading such materials near Lincoln Center.

[9][11] She exhibited some of these at the Museum of the City of New York,[6] and eventually donated her collection to several theatre history archives, including the Library of Congress.