Few details of Elizabeth's early life have been documented. She was born in the Caribbean Islands, where she received an excellent education, probably including a college degree. She moved to Boston in the 1870s, where she helped establish a library and became a public schoolteacher. Boston women organized some of the earliest women's suffrage associations and social reform groups. These groups attracted Elizabeth, who found that students in her own African American community needed more resources and support.

In 1882, Elizabeth married Howell N. Ensley. The couple moved to Washington, D.C., where they were associated with Howard University, the flagship college founded and attended primarily by African Americans. Some time in the early 1890s, the Ensleys decided to try their fortunes in the West, so they moved to Denver, Colorado, to start a new life.

The Ensleys arrived during exciting but troublesome times in Colorado. By 1892, signs of economic depression were already apparent, with an increasing number of unemployed miners and their families arriving in Denver without food or shelter. Elizabeth used her contacts with women's clubs in Boston and Washington to join Denver's relief efforts for the poor and the homeless.

On the brighter side, a group of Denver women had reorganized the state's suffrage organization, the Colorado Non-Partisan Equal Suffrage Association. They wanted to put a women's suffrage amendment on the November 1893 ballot and needed help. Ensley joined the campaign enthusiastically, feeling that she could organize black women and persuade black men to vote in favor of suffrage. She served as treasurer of the association, starting with a meager fund of just twenty-five dollars. Under her leadership, suffragists gained the financial backing they needed to carry out their successful campaign. On November 7, 1893, the suffrage referendum was approved by the all-male electorate by more than 6,000 votes.

Ensley did not stop to celebrate. She quickly organized the Colorado Colored Women's Republican Club to educate black women on why and how to vote. Ensley reported that the women "heroically helped their brothers to elect a representative to the legislature," black lawyer Joseph Stuart of Denver, in 1894. That same year, Colorado voters elected the first three female state legislators in the United States.

Ensley founded the Colorado Association of Colored Women's Clubs in 1904. This important network spearheaded community and educational programs, including the George Washington Carver Day Nursery. Ensley had already broken the color barrier when she served in the mostly white suffrage association. She continued in her role as a communicator to all groups of women by serving as the only black member of the predominantly white board of the Colorado Federation of Women's Clubs. Her organizational skill and adeptness with a diversity of women's groups made Ensley a living example of networking for social change.