I just got this DVD set and also read the liner notes and the status of the unknown actress. But Minnewanna is obviously played by Lottie Pickford, the actress sister of superstar, Mary Pickford. Check out photos of Lottie Pickford on various web sites.
Griffith is the most important director in the history of American films. That he was considered hopelessly old fashioned by the dawn on talkies is irrelevant. His early short films helped set the tone for the look and feel and attitudes toward Indians, cowboys, the American West, the Civil War, etc. While this film (at 15 minutes) is not dramatically moving, it IS important as an early look at Griffith's love of and attitudes toward history. Even in 1909 he was not afraid of portraying the settlers as "conquerors" any more than he was afraid to take an honest look at our Civil War period in THE BIRTH OF A NATION in 1915.