Many of Lennart's credits were star vehicles for the likes of Danny Kaye ("Merry Andrew" 1958), Doris Day ("Please Don't Eat the Daisies" 1960) and Esther Williams ("Skirts Ahoy!" 1952). Some of her best work came with atypically dramatic fare: "East Side West Side" (1949) gave Barbara Stanwyck a good workout; "The Inn of the Sixth Happiness" (1958) won plaudits for Ingrid Bergman and Robert Donat; and George Cukor's "A Life of Her Own" (1950) was a somewhat underrated showcase for Lana Turner and Ann Dvorak. Along similar lines was one of Lennart's finest efforts, the Oscar-nominated screenplay for "Love Me or Leave Me" (1955), a potently dramatic musical teaming Day with James Cagney, based on the life of 1930s torch singer Ruth Etting. Equally fine but more in keeping with Lennart's typically buoyant tone was another fine Oscar-nominated screenplay, this one an adaptation which resulted in the lovely tale of Australian sheepherders, "The Sundowners" (1960).
No case has been made by critics or academics for Lennart as a key example of the screenwriter as "auteur", but many of her screenplays do center upon women optimistically coping with careers, families and especially men who prove difficult because of possessiveness, addictions, finances, restlessness, or infidelity. For much of her career, she had focused upon screenplay writing, but Lennart the playwright enjoyed her biggest success and most enduring Broadway achievement when she took a few years off from movies to pen the musical biography of another iconic singer of the Jazz Age and the Depression. The smash "Funny Girl" (1964) told the story of Fanny Brice, clinched Barbra Streisand's stardom and was successfully adapted by Lennart for the 1968 film version. It also turned out to be her swan song, for Lennart was killed in a car crash in 1971.