Who is Mary Costa?

Recently I've been studying the score of Mozart's opera Cosi fan tutte and chose my companion to be a 1954 EMI recording, conducted by Herbert von Karajan.  I love Maestro Karajan's recording of the complete Beethoven symphonies and knew that this particular Cosi is regarded as one of his most successful Mozart endeavors on record.  The cast includes Elisabeth Schwarzkopf, Nan Merriman, [...]