Russian pianist, (b. 1853; d. 1942), born Adelina Eduardovna Gippius (Аделина Эдуардовна Гиппиус), known outside Russian as Adele Hippius.
Correspondence with Tchaikovsky
One letter from Tchaikovsky to Adele Hippius has survived, dating from 1877, and has been translated into English on this website:
One letter from Adele Hippius to the composer, also dating from 1877, has survived.