She spent part of her childhood with the Kirwans of Castle Hackett, County Galway, her mother's family, and drew on West of Ireland themes for many of her works.

According to Betty Webb Brewer, writing in 1983 for the journal of the Irish American Cultural Institute, Éire/Ireland: "An unflagging unionist, she recognised the rich literary potential in the native tradition and wrote novels with peasant heroes and heroines, Lawless depicted with equal sympathy the Anglo-Irish landholders."

Similarly, her initial opposition to female suffrage has been often read as an anti-feminist position (rather than a "feminism of difference"), yet much of her work makes a strong case for female autonomy, in financial and creative terms, and Lawless was a noted and popular writer in the "New Woman" movement which swept English fiction and journalism in the late nineteenth century.

Beginning in 1911, she lived with Lady Sarah Spencer, dedicatee of A Garden Diary (1901), at a house named Hazelhatch in Gomshall, Surrey.

Lawless wrote nineteen works of fiction, biography, history, nature studies and poetry, many of which were widely read at the time.

Her reputation was damaged by William Butler Yeats who accused her in a critique of having "an imperfect sympathy with the Celtic nature" and for adopting "theory invented by political journalists and forensic historians".

Her seventh book, Grania, about "a very queer girl leaping and dancing over the rocks of the sea" examined the misogyny of an Aran Island fishing society.

Unusually for such a strong Unionist, her Wild Geese poems (1902) became very popular and were widely quoted in nationalist circles, especially the lines: War-battered dogs are we, Fighters in every clime; Fillers of trench and of grave, Mockers bemocked by time.