Vining was born in Philadelphia, Pennsylvania, and was a graduate of Germantown Friends School and Bryn Mawr College, class of 1923. In 1925, she earned a degree in library science from the nearby Drexel Institute, and in 1926 she became a librarian at the University of North Carolina at Chapel Hill. In 1929, she married Morgan Fisher Vining, associate director of the Extension Division of the same university. The marriage ended in 1933 with her husband's death in a New York City automobile accident, in which she was severely injured. During her convalescence, she converted to the Quaker faith.

Vining soon became known as an author, primarily of children's books, and was awarded the 1943 Newbery Medal for Adam of the Road. She had authored eleven books by the end of World War II.

During the Allied occupation of Japan after the war, Vining was selected by Emperor Hirohito himself (and not the U.S. government, as is erroneously believed by some) to become a private tutor to Crown Prince Akihito, the heir apparent of the Imperial House of Japan. As part of her teaching program, she arranged for closely-supervised occasions when four Western teen-aged boys in Tokyo would get together to help the crown prince practice English conversation.

In addition to teaching English language skills, she also introduced the children of the Imperial Household, Prince Hitachi and princesses Kazuko, Atsuko, and Takako, to Western values and culture. She also lectured at Gakushuin University and at Tsuda College. For her work, she was awarded the Order of the Sacred Treasure, third class, shortly before her return to the United States in 1950.

After her return to the United States, Vining wrote a book about her experiences in Japan (Windows for the Crown Prince, 1952) and went on to author over 60 other works of fiction and non-fiction in her lifetime.