Edith Frances deBecker Sebald, 78, a former specialist for the Office of Strategic Services (OSS) in World War II and the widow of former U.S. ambassador to Burma William J. Sebald, died of an aneurysm Tuesday at her home in Naples, Fla.

The daughter of a British father and a Japanese mother, Mrs. Sebald was born in Kamakura, Japan. She was educated in this country and in England and graduated from a finsihing school in Boston.

While her husband was serving as a political adviser to Gen. Douglas MacArthur in World War II, Mrs. Sebald remained in Washington and worked as a consultant in psychological warfare for the OSS.

After the war, she accompanied her husband to Tokyo, where he served as chief of general headquarters of the Supreme Command for Allied Powers (SCAP) before being named ambassador to Burma in the mid-1950s.

Mrs. Sebald received national prominence in 1946 when she was "adopted" by the U.S. through a special Act of Congress. She had lost her Japanese citizenship when she married Mr. Sebald in 1927 and was unable to become a citizen of this country because of restrictions on Japanese immigration.

She and her husband, who died last year, lived in Washington before moving to Naples in 1966.

Mrs. Sebald was a painter and the author of a cookbook on Japanese cuisine. She had completed work on her memoirs shortly before her death.

There are no immediate survivors.