Educated at home by her mother, Donnelly began to write poetry at age nine, a hymn to the Blessed Virgin, which appeared in a child's paper.

Donnelly composed a number of poems during the early years of the American Civil War, several of which were published, often unattributed and without her permission.

[3] Encouraged by her friends and family to protect her claims to these poems, which often dealt with themes of loss and grief, she collected many of them in her first book, Out of Sweet Solitude, published in 1873.

Her poetry largely addresses Catholic and spiritual themes and she often composed poems to commemorate religious events and celebrations.

[3] Her funeral was held in the Cathedral Basilica of Saints Peter and Paul in Philadelphia, at which Archbishop Prendergast gave the final absolution.