Daughter of Dallas Vernon, a lawyer, and Kate Logan (Cummings) Halverstadt, a concert soprano.
Discovered by Samuel Goldwyn while she was appearing on Broadway.
From an early age she wanted to be a classical dancer, but in her mid-teens, after a walk-on bit as a prostitute in a summer stock production of "Seventh Heaven", she switched gears and began acting and dancing in stage musicals.
Graced a number of her husband's plays, including "Accent on Youth" (1934), "Young Madame Conti" (1936), "Madame Bovary" (adapted) (1937), "If I Were You" (1938), "The Jealous God" (1939), "Clutterbuck" (1946), "Return to Tyassi" (1950), "The Rape of the Belt" (191957) and "Public and Confidential" (1966).
Had two children: Jonathan and Jemina.
In 1974, the American-born Cummings, who resided in the UK for many decades, was made a Commander of the British Empire for her contributions to the British entertainment industry.
She was awarded the C.B.E. (Commander of the Order of the British Empire) in the 1974 Queen's Honours List for her services to drama.
Was a committee member of the Royal Court Theatre and the Arts Council.
Won Broadway's 1979 Tony Award as Best Actress (Play) for "Wings" in a tie with Carole Shelley for "The Elephant Man." Ms. Cummings recreated her Tony-winning performance in a television version with the same title, "American Playhouse: Wings (#2.11)" (1983).
Won the Tony Award (shared with Carole Shelley in "The Elephant Man"), an Obie Award, and a Drama Desk Award for her twilight role in "Wings" (1979).