From 1894, Jennness was engaged in mission work for girls of the
Cheyenne River Sioux Tribe, in
South Dakota. and in 1908, she was based in Flora,
Walworth County, South Dakota. Becoming well known as a talented and popular magazine writer, she was especially gifted in her stories and dialogues for children. She contributed to the "Zig Zag series", edited by
Hezekiah Butterworth. At one time, she held an editorial position with ''
The Youth's Companion''. She wrote "Fire Stories", "John Tryman", and made numerous other contributions to leading
eastern magazines. She was the author of,
Two Young Homesteaders, 1881;
Piokee and Her People, 1891;
Above the Range, 1896, ==Personal life==