Izola Forrester was born November 15, 1878, in Pascoag, Rhode Island. Her mother was Ogarita "Rita" Booth, a stage actress who believed herself to be the daughter of John Wilkes Booth, and used his last name. Her father was George Wallingford Hills, a Harvard College student. They never married. Ogarita Booth was briefly married to William Ross Wilson before marrying Alexander Henderson, who was a director of musicals and light operas. They had two children, Beatrice Henderson Clutts Colony (1885-1961) and Charles Henderson (1886-1888). Forrester often acted on stage with her mother, but for periods of her childhood, she lived with her maternal grandmother, Izola Martha Mills, her cousin, Hanson Pike Gilman, and with George and Harriet Forrester. Following Ogarita Henderson's death on April 12, 1892, Izola Forrester went to live permanently with the Forresters, who formally adopted her on January 6, 1893.

On October 28, 1899, Forrester married Reuben Merrified, a painter for Ringling Brothers Circus. They spent the early years of their marriage in Chicago before moving to New York City. The family also spent time in Canterbury, Connecticut. The Merrifields had five children: Arthur (1901-1983), Rita (1903-1921), Richard "Dick" (1905-1977), Beatrice (1906-1907), and Dorothy (born 1908). In 1913, Forrester left Merrifield to marry author, screenwriter, and playwright, Mann Page; they had three children, Izola (1914-2004), Marjorie "Peg" (born 1916), and Rosamond "Ros" (born 1918).

Forrester was a prolific writer whose articles appeared in magazines including Ainslee's, Munsey's Magazine, Red Book Magazine, and The Young Churchman . She also wrote several books for young girls including Those Preston Twins, Rook's Nest, The Girls of Bonnie Castle, and "Us Fellers", as well as the series featuring Polly Page and the Greenacre Girls. In 1937, she wrote This One Mad Act: The Unknown Story of John Wilkes Booth and His Family, in which she defended her belief that Booth was her grandfather. Forrester also wrote several silent movie screenplays including, The White Moth and a Café in Cairo .

In 1940, Forrester and her family moved to Keene, New Hampshire. She died on March 6, 1944.